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/package.json

@@ -17,6 +17,7 @@
 		"@sveltejs/kit": "^2.50.2",
 		"@sveltejs/vite-plugin-svelte": "^6.2.4",
 		"@tailwindcss/vite": "^4.2.1",
+		"@types/node": "^25.3.3",
 		"svelte": "^5.51.0",
 		"svelte-check": "^4.4.2",
 		"tailwindcss": "^4.2.1",