Implement Phases 1-5: skeleton, OAuth, categories, video sync/feed, playback

- FastAPI + PostgreSQL + Alembic + React/Vite skeleton, Docker Compose, healthcheck
- Google OAuth (single allowed account), encrypted refresh token storage
- Subscriptions sync with pagination, uploads playlist batch fetch
- Categories CRUD, many-to-many channel assignment, category filtering
- Video sync (playlistItems + videos.list batching), cached feed with cursor
  pagination, background scheduler (APScheduler)
- Video detail page with YouTube embed player
- SPA fallback routing, optimistic UI updates, client-side query caching

40 backend tests covering OAuth allow-list, sync idempotency, cascade deletes,
cursor pagination, and category filtering.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

frontend/package.json

@@ -0,0 +1,27 @@
+{
+  "name": "frontend",
+  "private": true,
+  "version": "0.0.0",
+  "type": "module",
+  "scripts": {
+    "dev": "vite",
+    "build": "tsc -b && vite build",
+    "lint": "oxlint",
+    "preview": "vite preview"
+  },
+  "dependencies": {
+    "@tanstack/react-query": "^5.103.1",
+    "react": "^19.2.8",
+    "react-dom": "^19.2.8",
+    "react-router-dom": "^7.18.4"
+  },
+  "devDependencies": {
+    "@types/node": "^24.13.3",
+    "@types/react": "^19.2.18",
+    "@types/react-dom": "^19.2.7",
+    "@vitejs/plugin-react": "^6.1.1",
+    "oxlint": "^1.81.0",
+    "typescript": "~6.0.2",
+    "vite": "^8.3.0"
+  }
+}