feat: add contact page with form handling and validation

- Implemented a contact page with a form for user inquiries.
- Added validation for form fields using Zod schema.
- Integrated PostgreSQL database for storing contact messages.
- Created necessary API endpoints for form submission.
- Added admin authentication and session management.
- Developed CGU, cookies policy, privacy policy, and legal mentions pages.
- Set up Docker configuration for PostgreSQL and application services.
- Enhanced UI with responsive design and accessibility features.

app/api/admin/login/route.ts

@@ -0,0 +1,29 @@
+import { NextResponse } from "next/server";
+import { createAdminToken, getAdminCookieName, getAdminCredentials } from "@/lib/admin-auth";
+
+export async function POST(request: Request) {
+  const body = (await request.json().catch(() => null)) as
+    | { username?: string; password?: string }
+    | null;
+
+  if (!body?.username || !body?.password) {
+    return NextResponse.json({ message: "Identifiants manquants." }, { status: 400 });
+  }
+
+  const credentials = getAdminCredentials();
+  if (body.username !== credentials.username || body.password !== credentials.password) {
+    return NextResponse.json({ message: "Identifiants invalides." }, { status: 401 });
+  }
+
+  const token = createAdminToken(body.username);
+  const response = NextResponse.json({ ok: true });
+  response.cookies.set(getAdminCookieName(), token, {
+    httpOnly: true,
+    sameSite: "lax",
+    secure: process.env.NODE_ENV === "production",
+    path: "/",
+    maxAge: 60 * 60 * 12,
+  });
+
+  return response;
+}