Analytics:
- Add video watch metrics section to shop dashboard (avg % played,
completion rate, seeks, rewinds, pauses, speed) with per-product
video breakdown table
- Add per-product analytics detail page at /s/{shop_id}/analytics/{product_id}
with views over time, video watch, traffic, devices, ring entries,
engagement, comment sentiment, and price history
- Product title links on shop analytics now go to per-product analytics
- Add get_sentiment_summary_for_product() helper
SPA fix:
- Update thumbnail image src and wrapping link href during DJ fade
- Clear stale extra thumbnails from previous product
- Add file_url to watch JSON for thumbnail-to-file links