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/src/components/VideoCard.tsx

@@ -0,0 +1,40 @@
+import { Link } from 'react-router-dom'
+import type { FeedVideoDto } from '../api/client'
+import { formatDuration, formatRelativeTime } from '../utils/format'
+
+interface Props {
+  video: FeedVideoDto
+}
+
+function VideoCard({ video }: Props) {
+  const duration = formatDuration(video.duration_seconds)
+  const href = `/video/${video.youtube_video_id}`
+
+  return (
+    <li className="video-card">
+      <Link to={href} className="video-thumbnail">
+        {video.thumbnail_url ? (
+          <img src={video.thumbnail_url} alt={video.title} />
+        ) : (
+          <div className="video-thumbnail-placeholder" />
+        )}
+        {duration && <span className="duration-badge">{duration}</span>}
+      </Link>
+      <div className="video-info">
+        <Link to={href} className="video-title" title={video.title}>
+          {video.title}
+        </Link>
+        <div className="video-meta">
+          {video.channel.title} · {formatRelativeTime(video.published_at)}
+        </div>
+        <div className="video-actions">
+          <Link to={href} className="button-link">
+            Смотреть
+          </Link>
+        </div>
+      </div>
+    </li>
+  )
+}
+
+export default VideoCard