feat(stage-10E): SquareSyncController + square()/multi() factories + KcBootstrap Square validation + ID conflation fix

Stage 10E - feat/square-catalog-sync-service-controller

P1.1 AppServices.square() / multi() factories (kell_web + kell_mobile)
P1.2 SquareCatalogSyncService ID conflation fix (squareCatalogObjectId lookup)
P1.4 SquareSyncController ChangeNotifier (SyncPhase, syncAll, reset, disposal guard)
P1.5 KcBootstrap Square credential validation with fallback warning

New files:
  feature_wordpress/lib/src/application/square_sync_controller.dart
  feature_wordpress/test/square_sync_controller_test.dart (18 tests)

Modified files:
  feature_wordpress/lib/src/domain/product_draft.dart (squareCatalogObjectId field)
  feature_wordpress/lib/src/application/square_catalog_sync_service.dart (ID conflation fix)
  feature_wordpress/lib/feature_wordpress.dart (barrel export)
  kell_web/lib/composition/app_services.dart (square/multi factories)
  kell_mobile/lib/composition/mobile_app_services.dart (square/multi factories)
  kell_web/test/composition/app_services_test.dart (+23 tests)
  kell_mobile/test/composition/mobile_app_services_test.dart (+23 tests)
  docs/development/build_execution_tracker.md

Test results: 537/537 feature_wordpress, 47/47 kell_web, 49/49 kell_mobile,
              34/34 core, 167/167 feature_inventory - 834 total, 0 failures
dart analyze --fatal-infos: no issues found across all 5 packages