Initial commit: SejeteralO water tarification platform

Full-stack app for participatory water pricing using Bezier curves.
- Backend: FastAPI + SQLAlchemy + SQLite with JWT auth
- Frontend: Nuxt 4 + TypeScript with interactive SVG editor
- Math engine: cubic Bezier tarification with Cardano solver
- Admin: commune management, household import, vote monitoring, CMS
- Citizen: interactive curve editor, vote submission
- Docker-compose deployment ready

Includes fixes for:
- Impact table snake_case/camelCase property mismatch
- CMS content backend API + frontend editor (was stub)
- Admin route protection middleware
- Public content display on commune page
- Vote confirmation page link fix

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/app/composables/useApi.ts

@@ -0,0 +1,67 @@
+/**
+ * Composable for API calls to the FastAPI backend.
+ */
+export function useApi() {
+  const config = useRuntimeConfig()
+  const baseURL = config.public.apiBase as string
+
+  function getToken(): string | null {
+    if (import.meta.client) {
+      return localStorage.getItem('sejeteralo_token')
+    }
+    return null
+  }
+
+  async function apiFetch<T>(
+    path: string,
+    options: RequestInit = {},
+  ): Promise<T> {
+    const headers: Record<string, string> = {
+      ...(options.headers as Record<string, string> || {}),
+    }
+
+    const token = getToken()
+    if (token) {
+      headers['Authorization'] = `Bearer ${token}`
+    }
+
+    if (options.body && !(options.body instanceof FormData)) {
+      headers['Content-Type'] = 'application/json'
+    }
+
+    let response: Response
+    try {
+      response = await fetch(`${baseURL}${path}`, {
+        ...options,
+        headers,
+      })
+    } catch (err) {
+      throw new Error(`Impossible de contacter le serveur (${baseURL}). Vérifiez que le backend est lancé.`)
+    }
+
+    if (!response.ok) {
+      const error = await response.json().catch(() => ({ detail: response.statusText }))
+      throw new Error(error.detail || `Erreur API ${response.status}`)
+    }
+
+    const text = await response.text()
+    if (!text) return {} as T
+    return JSON.parse(text)
+  }
+
+  return {
+    get: <T>(path: string) => apiFetch<T>(path),
+    post: <T>(path: string, body?: unknown) =>
+      apiFetch<T>(path, {
+        method: 'POST',
+        body: body instanceof FormData ? body : JSON.stringify(body),
+      }),
+    put: <T>(path: string, body?: unknown) =>
+      apiFetch<T>(path, {
+        method: 'PUT',
+        body: JSON.stringify(body),
+      }),
+    delete: <T>(path: string) =>
+      apiFetch<T>(path, { method: 'DELETE' }),
+  }
+}