feat: stages module, mobility frontend, theme toggle, employeeOnly access control

- Add stages module with full CRUD API and admin overview island
- Add mobility overview island (Liste, Kanban, Detail CRUD views)
- Add contract PDF upload/download endpoints for mobilites
- Add light/dark theme toggle in header
- Add employeeOnly flag to hide entire modules from students (admin, students, stages)
- Add read-only GET endpoints for modules/ues/ue-modules in notes module
- Add [slug].tsx catch-all routes for direct URL navigation
- Replace old mobility table with mobilites + stages schema (migration 0004)
- Allow students to create mobilites and upload contracts
- Redirect authenticated users from / to /apps catalog

routes/(apps)/notes/api/ues.ts

@@ -0,0 +1,12 @@
+import { Handlers } from "$fresh/server.ts";
+import { db } from "$root/databases/db.ts";
+import { ues } from "$root/databases/schema.ts";
+
+export const handler: Handlers = {
+  async GET() {
+    const rows = await db.select().from(ues);
+    return new Response(JSON.stringify(rows), {
+      headers: { "content-type": "application/json" },
+    });
+  },
+};