feat: Add backend tests with full cache initialization

- Add .env.test with test credentials and company config
- Add pytest fixtures for cache initialization (temp SQLite)
- Add test_api_real.py (18 tests) - API endpoint tests
- Add test_cache_real.py (8 tests) - Cache system tests
- Add test_services_real.py (9 tests) - Service layer tests
- Use company 110 (MARIUSM_AUTO) - only schema with full data in TEST

All 35 backend tests pass.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

reports-app/backend/tests/__init__.py

@@ -0,0 +1 @@
+# Backend Tests Package