Refactor E2E tests and fixtures for improved readability and consistency

- Reformatted assertions in `test_database_workflows.py` for better readability.
- Refactored `postgres_url` transformation logic in `conftest.py` for improved clarity.
- Adjusted import handling in `test_api_contracts.py` to streamline usage of Hypothesis and Schemathesis libraries.

backend/tests/e2e/test_api_contracts.py

@@ -15,8 +15,8 @@ Note: Schemathesis v4.x API - filtering is done via include/exclude methods.
 import pytest
 
 try:
+    from hypothesis import settings
     from schemathesis import openapi
-    from hypothesis import Phase, settings
 
     SCHEMATHESIS_AVAILABLE = True
 except ImportError: