feat: Implement repost/boost API, profile layout persistence, feed algorithm wiring, and legacy cleanup
Backend:
- Add repost_handler.go with full CRUD (create, boost, delete, report, trending, amplification analytics)
- Add profile_layout_handler.go for profile widget layout persistence (GET/PUT)
- Wire FeedAlgorithmService into main.go as 15-min background score refresh job
- Fix follow_handler.go (broken interface, dead query pattern, naming conflict)
- Add DB migration for reposts, repost_reports, profile_layouts, post_feed_scores tables
- Add engagement count columns to posts table for feed algorithm
- Remove stale Supabase comments from auth middleware
- Delete cmd/supabase-migrate/ directory (legacy migration tool)
Flutter:
- Fix all repost_service.dart API paths (were doubling /api/ prefix against base URL)
- Rename forceResetBrokenKeys() -> resetIdentityKeys() in E2EE services
- Remove dead _forceResetBrokenKeys method from secure_chat_screen.dart
- Implement _navigateToProfile(), _navigateToHashtag(), _navigateToUrl() in sojorn_rich_text.dart
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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