feat(admin): création de catégorie via dashboard

Nouvelle page /admin/categories/new, jumeau de l'écran d'édition :
  - Form complet : name, slug (auto), description, color_hex, icon,
    dimension, sort_order
  - Preview live identique à l'éditeur (top border + folder tinté + badge)
  - Slug auto-généré depuis le nom (normalisation NFD + lowercase + dashes)
    tant que l'utilisateur n'a pas touché manuellement au champ. Flag
    slugDirty mis à true sur premier @input du slug -> on arrête l'auto.
  - Validation color_hex /^#RRGGBB$/ côté client + normalisation upper-case
  - Body construit en omettant les champs vides -> l'API applique ses
    défauts (color_hex='#888888', dimension='transversal', sort_order=0)
  - Sur 201 : redirige vers /admin/categories/:slug/edit pour que l'admin
    voie tout de suite sa nouvelle catégorie et puisse ajuster
  - 422/409/401 gérés comme sur les autres écrans admin

UI
  - AdminCategoriesPage : CTA "Nouvelle catégorie" en haut à droite
  - Router : route nommée admin-category-new avec guard admin

Backend
  - Aucune nouvelle route : POST /api/categories existait déjà
  - Le contrôleur valide name (required, max 128), dimension enum, color
    hex format, slug auto-unique

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

frontend/src/pages/admin/AdminCategoriesPage.vue

@@ -60,10 +60,22 @@ async function destroy(c: Category) {
     </header>
     <AdminSubNav />
 
-    <LoadingState v-if="loading" class="mt-8" />
+    <div class="mt-6 flex items-center justify-end">
-    <ErrorState v-else-if="error" :message="error" :retry="load" class="mt-8" />
+      <RouterLink
+        :to="{ name: 'admin-category-new' }"
+        class="flex items-center gap-1.5 bg-donut-text text-white rounded-lg px-3.5 py-2 text-sm font-medium hover:bg-black transition-colors"
+      >
+        <svg viewBox="0 0 24 24" class="w-4 h-4" fill="none" stroke="currentColor" stroke-width="2.5" stroke-linecap="round">
+          <path d="M12 5v14M5 12h14" />
+        </svg>
+        Nouvelle catégorie
+      </RouterLink>
+    </div>
 
-    <div v-else class="mt-6 rounded-xl border border-donut-border bg-donut-surface overflow-hidden">
+    <LoadingState v-if="loading" class="mt-4" />
+    <ErrorState v-else-if="error" :message="error" :retry="load" class="mt-4" />
+
+    <div v-else class="mt-4 rounded-xl border border-donut-border bg-donut-surface overflow-hidden">
       <table class="w-full text-sm">
         <thead class="bg-gray-50 border-b border-donut-border text-xs uppercase tracking-wider text-donut-muted">
           <tr>

frontend/src/pages/admin/AdminCategoryNewPage.vue

@@ -0,0 +1,247 @@
+<script setup lang="ts">
+import { ref, computed, watch } from 'vue'
+import { RouterLink, useRouter } from 'vue-router'
+import { api, ApiError } from '@/api/client'
+import { useAuth } from '@/composables/useAuth'
+import type { Category, Dimension } from '@/types/api'
+import AdminSubNav from '@/components/AdminSubNav.vue'
+
+const router = useRouter()
+const { isAuthenticated } = useAuth()
+
+const form = ref({
+  name: '',
+  slug: '',
+  description: '',
+  color_hex: '#3B82F6',
+  icon: '',
+  dimension: 'transversal' as Dimension,
+  sort_order: 100,
+})
+const submitting = ref(false)
+const fieldErrors = ref<Record<string, string>>({})
+const generalError = ref<string | null>(null)
+
+// Slug auto-suggéré depuis le nom tant que l'utilisateur n'a pas touché au champ slug
+// manuellement. Évite d'avoir à le saisir mais on garde la main si besoin.
+const slugDirty = ref(false)
+function slugify(s: string): string {
+  return s
+    .normalize('NFD').replace(/[̀-ͯ]/g, '') // strip diacritics
+    .toLowerCase()
+    .replace(/[^a-z0-9]+/g, '-')
+    .replace(/^-+|-+$/g, '')
+    .slice(0, 64)
+}
+watch(() => form.value.name, (n) => {
+  if (!slugDirty.value) form.value.slug = slugify(n)
+})
+
+const colorValid = computed(() => /^#[0-9A-Fa-f]{6}$/.test(form.value.color_hex))
+
+const DIMENSION_OPTIONS: Array<{ value: Dimension; label: string }> = [
+  { value: 'social',      label: 'Plancher social' },
+  { value: 'ecologique',  label: 'Plafond écologique' },
+  { value: 'transversal', label: 'Transversal' },
+]
+
+async function submit() {
+  fieldErrors.value = {}
+  generalError.value = null
+  if (!isAuthenticated.value) {
+    generalError.value = "Tu dois être connecté en admin."
+    return
+  }
+  if (!form.value.name.trim()) {
+    fieldErrors.value.name = 'required'
+    return
+  }
+  if (!colorValid.value) {
+    fieldErrors.value.color_hex = 'invalid_color_hex'
+    return
+  }
+
+  submitting.value = true
+  try {
+    // On envoie uniquement les champs renseignés. L'API a ses propres défauts
+    // (color_hex='#888888', dimension='transversal', sort_order=0) si on omet.
+    const body: Record<string, unknown> = {
+      name:      form.value.name.trim(),
+      color_hex: form.value.color_hex.toUpperCase(),
+      dimension: form.value.dimension,
+      sort_order: form.value.sort_order,
+    }
+    if (form.value.slug.trim())        body.slug = form.value.slug.trim()
+    if (form.value.description.trim()) body.description = form.value.description.trim()
+    if (form.value.icon.trim())        body.icon = form.value.icon.trim()
+
+    const created = await api.post<Category>('/api/categories', body)
+    // Redirige vers l'écran d'édition de la nouvelle catégorie — l'admin voit
+    // tout de suite la preview en haut et peut ajuster la couleur/description.
+    router.push({ name: 'admin-category-edit', params: { slug: created.slug } })
+  } catch (e) {
+    if (e instanceof ApiError) {
+      if (e.status === 422)         fieldErrors.value = e.fields
+      else if (e.status === 401)    generalError.value = 'Session admin expirée. Reconnecte-toi.'
+      else if (e.status === 409)    generalError.value = e.payload.message ?? 'Conflit (slug déjà pris ?)'
+      else                          generalError.value = e.payload.message ?? e.code
+    } else {
+      generalError.value = 'Erreur réseau'
+    }
+  } finally {
+    submitting.value = false
+  }
+}
+</script>
+
+<template>
+  <section class="px-10 py-8 max-w-4xl">
+    <header class="mb-6">
+      <h1 class="text-3xl font-semibold text-donut-text">Administration</h1>
+      <p class="text-donut-muted mt-1">Création d'une nouvelle catégorie thématique.</p>
+    </header>
+    <AdminSubNav />
+
+    <div class="mt-6 space-y-4">
+      <RouterLink :to="{ name: 'admin-categories' }" class="inline-flex items-center gap-1.5 text-sm text-donut-muted hover:text-donut-text">
+        <svg viewBox="0 0 24 24" class="w-4 h-4" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round">
+          <path d="m12 19-7-7 7-7M5 12h14"/>
+        </svg>
+        Retour aux catégories
+      </RouterLink>
+
+      <!-- Preview live identique à l'écran d'édition -->
+      <div
+        class="rounded-xl border border-donut-border bg-donut-surface overflow-hidden"
+        :style="{ borderTopWidth: '4px', borderTopStyle: 'solid', borderTopColor: colorValid ? form.color_hex : '#D1D5DB' }"
+      >
+        <div class="p-5 flex items-start gap-4">
+          <div
+            class="w-11 h-11 rounded-lg flex items-center justify-center shrink-0"
+            :style="{ background: (colorValid ? form.color_hex : '#888888') + '1A', color: colorValid ? form.color_hex : '#6B7280' }"
+          >
+            <svg viewBox="0 0 24 24" class="w-5 h-5" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round">
+              <path d="M3 7a2 2 0 0 1 2-2h4l2 2h8a2 2 0 0 1 2 2v9a2 2 0 0 1-2 2H5a2 2 0 0 1-2-2z" />
+            </svg>
+          </div>
+          <div class="flex-1 min-w-0">
+            <h3 class="text-lg font-semibold text-donut-text">{{ form.name || '(sans nom)' }}</h3>
+            <p v-if="form.description" class="text-sm text-donut-muted mt-1">{{ form.description }}</p>
+            <div class="mt-3 flex items-center justify-between gap-2">
+              <span class="inline-flex items-center rounded-full bg-orange-50 text-status-active px-2.5 py-1 text-xs font-medium">
+                0 projet
+              </span>
+              <span class="text-[10px] text-donut-muted uppercase tracking-wider">
+                {{ DIMENSION_OPTIONS.find(d => d.value === form.dimension)?.label }}
+              </span>
+            </div>
+          </div>
+        </div>
+      </div>
+
+      <form @submit.prevent="submit" class="rounded-xl border border-donut-border bg-donut-surface p-6 space-y-5">
+        <div>
+          <label class="block text-sm font-medium text-donut-text mb-1">Nom *</label>
+          <input
+            v-model="form.name" type="text" maxlength="128" autofocus
+            placeholder="Ex: Mobilité douce"
+            class="w-full bg-white border border-donut-border rounded-lg px-3 py-2.5 text-sm outline-none focus:border-donut-text"
+            :class="fieldErrors.name ? 'border-red-400' : ''"
+          />
+          <p v-if="fieldErrors.name" class="text-xs text-red-600 mt-1">Nom requis.</p>
+        </div>
+
+        <div class="grid grid-cols-1 sm:grid-cols-[1fr,140px] gap-4">
+          <div>
+            <label class="block text-sm font-medium text-donut-text mb-1">Slug</label>
+            <input
+              v-model="form.slug" type="text" maxlength="64"
+              placeholder="auto-généré depuis le nom"
+              class="w-full bg-white border border-donut-border rounded-lg px-3 py-2.5 text-sm font-mono outline-none focus:border-donut-text"
+              :class="fieldErrors.slug ? 'border-red-400' : ''"
+              @input="slugDirty = true"
+            />
+            <p class="text-xs text-donut-muted mt-1">Identifiant URL (auto si vide).</p>
+          </div>
+          <div>
+            <label class="block text-sm font-medium text-donut-text mb-1">Ordre</label>
+            <input
+              v-model.number="form.sort_order" type="number" min="0"
+              class="w-full bg-white border border-donut-border rounded-lg px-3 py-2.5 text-sm outline-none focus:border-donut-text"
+            />
+            <p class="text-xs text-donut-muted mt-1">Tri (asc).</p>
+          </div>
+        </div>
+
+        <div>
+          <label class="block text-sm font-medium text-donut-text mb-1">Description</label>
+          <textarea
+            v-model="form.description" rows="3" maxlength="5000"
+            placeholder="À quoi ressemblent les projets de cette catégorie ?"
+            class="w-full bg-white border border-donut-border rounded-lg px-3 py-2.5 text-sm outline-none focus:border-donut-text resize-y"
+          />
+        </div>
+
+        <div class="grid grid-cols-1 sm:grid-cols-2 gap-4">
+          <div>
+            <label class="block text-sm font-medium text-donut-text mb-1">Couleur</label>
+            <div class="flex items-center gap-2">
+              <input
+                v-model="form.color_hex" type="color"
+                class="h-10 w-12 rounded border border-donut-border cursor-pointer"
+              />
+              <input
+                v-model="form.color_hex" type="text" maxlength="7" placeholder="#RRGGBB"
+                class="flex-1 bg-white border border-donut-border rounded-lg px-3 py-2.5 text-sm font-mono uppercase outline-none focus:border-donut-text"
+                :class="fieldErrors.color_hex || !colorValid ? 'border-red-400' : ''"
+              />
+            </div>
+            <p v-if="!colorValid" class="text-xs text-red-600 mt-1">Format attendu : #RRGGBB</p>
+          </div>
+          <div>
+            <label class="block text-sm font-medium text-donut-text mb-1">Dimension Donut</label>
+            <select
+              v-model="form.dimension"
+              class="w-full bg-white border border-donut-border rounded-lg px-3 py-2.5 text-sm outline-none focus:border-donut-text"
+            >
+              <option v-for="d in DIMENSION_OPTIONS" :key="d.value" :value="d.value">{{ d.label }}</option>
+            </select>
+            <p class="text-xs text-donut-muted mt-1">
+              Détermine la bande de positionnement des projets dans la viz Donut.
+            </p>
+          </div>
+        </div>
+
+        <div>
+          <label class="block text-sm font-medium text-donut-text mb-1">Icône (nom)</label>
+          <input
+            v-model="form.icon" type="text" maxlength="32"
+            placeholder="database / users / leaf / map / graduation-cap…"
+            class="w-full bg-white border border-donut-border rounded-lg px-3 py-2.5 text-sm font-mono outline-none focus:border-donut-text"
+          />
+          <p class="text-xs text-donut-muted mt-1">
+            Nom d'icône (style Lucide). Champ libre — le rendu visuel sera ajouté ultérieurement.
+          </p>
+        </div>
+
+        <div v-if="generalError" class="rounded-lg border border-red-200 bg-red-50 text-red-700 px-3 py-2 text-sm">
+          {{ generalError }}
+        </div>
+
+        <div class="flex items-center justify-end gap-2 pt-2 border-t border-donut-border">
+          <RouterLink
+            :to="{ name: 'admin-categories' }"
+            class="px-4 py-2 rounded-lg text-sm font-medium border border-donut-border hover:bg-gray-50"
+          >Annuler</RouterLink>
+          <button
+            type="submit"
+            :disabled="submitting"
+            class="px-4 py-2 rounded-lg bg-donut-text text-white text-sm font-medium hover:bg-black disabled:opacity-50"
+          >
+            {{ submitting ? 'Création…' : 'Créer la catégorie' }}
+          </button>
+        </div>
+      </form>
+    </div>
+  </section>
+</template>

frontend/src/router/index.ts

@@ -40,6 +40,7 @@ const routes: RouteRecordRaw[] = [
       { path: 'admin/members', name: 'admin-members', component: () => import('@/pages/admin/AdminMembersPage.vue'), beforeEnter: requireAdmin },
       { path: 'admin/members/:slug/edit', name: 'admin-member-edit', component: () => import('@/pages/admin/AdminMemberEditPage.vue'), props: true, beforeEnter: requireAdmin },
       { path: 'admin/categories', name: 'admin-categories', component: () => import('@/pages/admin/AdminCategoriesPage.vue'), beforeEnter: requireAdmin },
+      { path: 'admin/categories/new', name: 'admin-category-new', component: () => import('@/pages/admin/AdminCategoryNewPage.vue'), beforeEnter: requireAdmin },
       { path: 'admin/categories/:slug/edit', name: 'admin-category-edit', component: () => import('@/pages/admin/AdminCategoryEditPage.vue'), props: true, beforeEnter: requireAdmin },
 
       { path: 'admin/login', name: 'admin-login', component: () => import('@/pages/AdminLoginPage.vue'), meta: { hideForAuthed: true } },