Replace direct *pgxpool.Pool usage with PoolProxy wrapper across the entire backend:
- db.DB renamed to db.Conn (*pgxpool.Pool -> *PoolProxy)
- JWT functions now accept context.Context instead of using context.Background()
- Handler DB calls route through PoolProxy for per-test transaction support
- Fixture/helper/testdb functions accept Querier interface for decoupling
- Query ordering fixed in bookings handlers: COUNT after data query to avoid pgx conn busy
- Time truncation fixed: time.Date instead of Truncate(24*time.Hour) for week start calc
- testmain_test.go files updated with SeedBaseline and NewPoolProxy
Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)
Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>
- Add TestMain to all 10 test packages (schema DROP+CREATE runs once per package)
- Convert per-test setupTestDB to resetTestData (TRUNCATE only, ~60% faster)
- Add 3 missing tables to TruncateTables (booking_edit_requests, exceptional_group_applications, business_settings)
- Remove dead truncateDiscountTables helper
- Consolidate discount_test.go into package bookings (was external test package)
- Update testutils.SetupTestDB to truncate-only
- Fix unused imports across user, bookings, and handlers packages
- Verify: 286 passing, 2 skipped, 0 failures with -count=2 (no state leakage)