Add video chapter/timeline navigation feature

Implement timeline chapters for webinar and bootcamp videos with click-to-jump functionality:

**Components:**
- VideoPlayerWithChapters: Plyr.io-based player with chapter support
- TimelineChapters: Clickable chapter markers with active state
- ChaptersEditor: Admin UI for managing video chapters

**Features:**
- YouTube videos: Clickable timestamps that jump to specific time
- Embed videos: Static timeline display (non-clickable)
- Real-time chapter tracking during playback
- Admin-defined accent color for Plyr theme
- Auto-hides timeline when no chapters configured

**Database:**
- Add chapters JSONB column to products table (webinars)
- Add chapters JSONB column to bootcamp_lessons table
- Create indexes for faster queries

**Updated Pages:**
- WebinarRecording: Two-column layout (video + timeline)
- Bootcamp: Per-lesson chapter support
- AdminProducts: Chapter editor for webinars
- CurriculumEditor: Chapter editor for lessons

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

package.json

@@ -62,6 +62,7 @@
     "lowlight": "^3.3.0",
     "lucide-react": "^0.462.0",
     "next-themes": "^0.3.0",
+    "plyr-react": "^6.0.0",
     "qrcode.react": "^4.2.0",
     "react": "^18.3.1",
     "react-day-picker": "^8.10.1",