- Add upsertGlobalItemSchema and bulkUpsertGlobalItemsSchema to schemas.ts
- Add UpsertGlobalItemInput and BulkUpsertGlobalItemsInput types to types.ts
- Implement upsertGlobalItem with onConflictDoUpdate and tag sync
- Implement bulkUpsertGlobalItems processing array in single transaction
- Fix migration 0003 to only add new columns + unique constraint
- All 21 tests pass including 8 new upsert operation tests