feat(admin): add admin panel with user management, daily puzzle CRUD, and activity graph

- Add admin page at /admin (restricted to ADMIN_EMAIL via proxy)
- Implement user ban/unban and deletion
- Add daily puzzle creation, modification, deletion
- Include 14-day activity chart with hover details
- Add User.banned field to schema and migrate database
- Block banned users from logging in
- Add ADMIN_EMAIL to .env.local configuration
- Update Prisma client after schema changes

pnpm-lock.yaml

@@ -8,12 +8,18 @@ importers:
 
   .:
     dependencies:
+      '@panva/hkdf':
+        specifier: ^1.2.1
+        version: 1.2.1
       '@prisma/client':
         specifier: ^7.7.0
         version: 7.7.0(prisma@7.7.0(@types/react-dom@19.2.3(@types/react@19.2.14))(@types/react@19.2.14)(better-sqlite3@12.8.0)(react-dom@19.2.4(react@19.2.4))(react@19.2.4)(typescript@5.9.3))(typescript@5.9.3)
       bcryptjs:
         specifier: ^3.0.3
         version: 3.0.3
+      jose:
+        specifier: ^6.2.2
+        version: 6.2.2
       next:
         specifier: 16.2.3
         version: 16.2.3(@babel/core@7.29.0)(react-dom@19.2.4(react@19.2.4))(react@19.2.4)