fix(loyalty): resolve critical production readiness issues

- Add pessimistic locking (SELECT FOR UPDATE) on card write operations
  to prevent race conditions in stamp_service and points_service
- Replace 16 console.log/error/warn calls with LogConfig.createLogger()
  in 3 storefront JS files (dashboard, history, enroll)
- Delete all stale lu.json locale files across 8 modules (lb is the
  correct ISO 639-1 code for Luxembourgish)
- Update architecture rules and docs to reference lb.json not lu.json
- Add production-readiness.md report for loyalty module

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docs/development/creating-modules.md

@@ -164,7 +164,7 @@ app/modules/mymodule/
 │   ├── en.json
 │   ├── de.json
 │   ├── fr.json
-│   └── lu.json
+│   └── lb.json
 │
 ├── tasks/                   # Celery tasks (auto-discovered)
 │   ├── __init__.py          # REQUIRED for discovery
@@ -539,7 +539,7 @@ python scripts/validate/validate_architecture.py
 - [ ] Create `exceptions.py`
 - [ ] Create routes with `router` variable
 - [ ] Create templates with namespace prefix
-- [ ] Create locales (en, de, fr, lu)
+- [ ] Create locales (en, de, fr, lb)
 - [ ] Create `config.py` if module needs environment settings (optional)
 - [ ] Create `migrations/versions/` with `__init__.py` files if module has database tables
 - [ ] Create `docs/index.md` with module overview (see [Module Documentation](module-documentation.md))