feat: add admin REST API layer for frontend management panel

Implement JWT-protected /admin/* routes on the relay server:
- Auth: login, logout, me, setup/status, setup/init (first-time config)
- Dashboard: stats overview (connections, devices, cookies, domains)
- Cookies: paginated list with domain/search filter, detail, delete, batch delete
- Devices: list with online status, revoke
- Settings: get/update (sync interval, max devices, theme)

Uses scrypt for password hashing and jsonwebtoken for JWT.
Adds listAll/revoke to DeviceRegistry, getAll/getById/deleteById to CookieBlobStore,
disconnect to ConnectionManager. Updates frontend to use /admin/* endpoints.

All 38 existing tests pass.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

package.json

@@ -12,17 +12,24 @@
     "test:watch": "vitest",
     "typecheck": "tsc --noEmit"
   },
-  "keywords": ["cookies", "sync", "encryption", "browser-extension"],
+  "keywords": [
+    "cookies",
+    "sync",
+    "encryption",
+    "browser-extension"
+  ],
   "author": "Rc707Agency",
   "license": "MIT",
   "type": "commonjs",
   "dependencies": {
+    "jsonwebtoken": "^9.0.3",
     "sodium-native": "^5.1.0",
     "typescript": "^5.9.3",
     "uuid": "^13.0.0",
     "ws": "^8.19.0"
   },
   "devDependencies": {
+    "@types/jsonwebtoken": "^9.0.10",
     "@types/node": "^25.5.0",
     "@types/sodium-native": "^2.3.9",
     "@types/uuid": "^10.0.0",