refactor: remove Redis dependencies from frontend authentication

- Replace Redis/Redlock with in-memory cache for token management
- Remove @vercel/kv, ioredis, and redlock dependencies from package.json
- Implement simple lock mechanism for concurrent token refresh prevention
- Use Map-based cache with TTL for token storage
- Maintain same authentication flow without external dependencies

This simplifies the infrastructure requirements and removes the need for
Redis while maintaining the same functionality through in-memory caching.

www/package.json

@@ -19,14 +19,12 @@
     "@sentry/nextjs": "^7.77.0",
     "@tanstack/react-query": "^5.85.5",
     "@vercel/edge-config": "^0.4.1",
-    "@vercel/kv": "^2.0.0",
     "@whereby.com/browser-sdk": "^3.3.4",
     "autoprefixer": "10.4.20",
     "axios": "^1.8.2",
     "eslint": "^9.33.0",
     "eslint-config-next": "^14.2.31",
     "fontawesome": "^5.6.3",
-    "ioredis": "^5.4.1",
     "jest-worker": "^29.6.2",
     "lucide-react": "^0.525.0",
     "next": "^14.2.30",
@@ -44,7 +42,6 @@
     "react-markdown": "^9.0.0",
     "react-qr-code": "^2.0.12",
     "react-select-search": "^4.1.7",
-    "redlock": "^5.0.0-beta.2",
     "sass": "^1.63.6",
     "simple-peer": "^9.11.1",
     "tailwindcss": "^3.3.2",