feat: secure admin panel with Supabase auth + course management CRUD

- Replace ADMIN_SECRET query param with proper Supabase auth + is_admin flag
- Add admin layout with auth check (redirects non-admin to /)
- Add AdminShell component with sidebar navigation (Dashboard, Candidatures, Cours)
- Add admin dashboard with stats (candidatures, users, modules)
- Add admin candidatures page with filters and approve/reject
- Add admin course management page (create, edit, delete, publish/unpublish)
- Add API routes: GET/POST /api/admin/modules, GET/PUT/DELETE /api/admin/modules/[id]
- Add verifyAdmin() helper for API route protection
- Update database types with is_admin on profiles

https://claude.ai/code/session_01H2aRGDaKgarPvhay2HxN6Y

app/api/admin/modules/route.ts

@@ -0,0 +1,65 @@
+import { NextResponse } from "next/server";
+import { createAdminClient } from "@/lib/supabase/server";
+import { verifyAdmin, isAdminError } from "@/lib/admin";
+
+export const runtime = "nodejs";
+
+// GET /api/admin/modules - Lister tous les modules (admin)
+export async function GET() {
+  const auth = await verifyAdmin();
+  if (isAdminError(auth)) {
+    return NextResponse.json({ error: auth.error }, { status: auth.status });
+  }
+
+  const supabase = createAdminClient();
+
+  const { data, error } = await supabase
+    .from("modules")
+    .select("*")
+    .order("week_number", { ascending: true })
+    .order("order_index", { ascending: true });
+
+  if (error) {
+    return NextResponse.json({ error: error.message }, { status: 500 });
+  }
+
+  return NextResponse.json({ modules: data });
+}
+
+// POST /api/admin/modules - Créer un nouveau module
+export async function POST(request: Request) {
+  const auth = await verifyAdmin();
+  if (isAdminError(auth)) {
+    return NextResponse.json({ error: auth.error }, { status: auth.status });
+  }
+
+  const body = await request.json();
+  const { title, description, week_number, order_index, content_type, content_url, duration_minutes, is_published } = body;
+
+  if (!title || !week_number) {
+    return NextResponse.json({ error: "Titre et semaine obligatoires." }, { status: 400 });
+  }
+
+  const supabase = createAdminClient();
+
+  const { data, error } = await supabase
+    .from("modules")
+    .insert({
+      title,
+      description: description || null,
+      week_number,
+      order_index: order_index ?? 0,
+      content_type: content_type || null,
+      content_url: content_url || null,
+      duration_minutes: duration_minutes ?? null,
+      is_published: is_published ?? false,
+    } as never)
+    .select()
+    .single();
+
+  if (error) {
+    return NextResponse.json({ error: error.message }, { status: 500 });
+  }
+
+  return NextResponse.json({ module: data }, { status: 201 });
+}