- Add DATABASE_READ_URL config and InitReadReplica in database package
- Add ForRead() helper for read-only handler routing
- Update TrackService and TrackSearchService to use read replica for reads
- Document setup in DEPLOYMENT_GUIDE.md and .env.template
- Deleted apps/web/src/utils/optimisticStoreUpdates.ts (unused file)
- File was unused - no imports found in codebase
- Mutations already use React Query's onMutate pattern
- No TypeScript errors after deletion
- Actions 4.4.1.2 and 4.4.1.3 complete