feat(auth): add user authentication with roles, HMAC-signed cookies, and login/register UI

- Add `users` PocketBase collection (username, password_hash, role, created)
- Implement HMAC-SHA256 signed cookie auth in hooks.server.ts; token payload is userId:username:role
- Add User type, getUserByUsername, createUser (scrypt), loginUser (timing-safe) to pocketbase.ts
- Add login/register page with tabbed form UI and server actions
- Add logout route that clears the auth cookie
- Add layout.server.ts auth guard: redirect unauthenticated users to /login
- Extend App.Locals and App.PageData with role field
- Add AUTH_SECRET, POCKETBASE_ADMIN_EMAIL/PASSWORD to .env.example
- Install @types/node for Node crypto/scrypt types

ui/.env.example

@@ -8,6 +8,13 @@ SCRAPER_API_URL=http://localhost:8080
 # Public URL of PocketBase (used by SvelteKit server-side load functions)
 POCKETBASE_URL=http://localhost:8090
 
+# PocketBase admin credentials (server-side only, never exposed to browser)
+POCKETBASE_ADMIN_EMAIL=admin@libnovel.local
+POCKETBASE_ADMIN_PASSWORD=changeme123
+
 # Public-facing MinIO URL (used to rewrite presigned URLs for the browser)
 # In dev this is localhost; in prod set to your MinIO public domain
 PUBLIC_MINIO_PUBLIC_URL=http://localhost:9000
+
+# Secret used to sign auth tokens stored in cookies (generate with: openssl rand -hex 32)
+AUTH_SECRET=change_this_to_a_long_random_secret