fix: Eliminate all 111 test warnings by fixing root causes

- Replace deprecated datetime.utcnow() with datetime.now(timezone.utc)
  across all domain models, services, infrastructure, and test files
- Add missing timezone imports to all affected files
- Fix pytest.ini configuration format from [tool:pytest] to [pytest]
- Remove warning suppressions to expose actual issues
- Ensure proper pytest marker registration for smoke tests

Results:
- 305 passed, 2 skipped, 0 warnings (down from 111 warnings)
- All functionality preserved with modern datetime API usage
- Improved code quality by addressing root causes vs suppression

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

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

infrastructure/repositories/gitea_repository.py

@@ -9,7 +9,7 @@ import asyncio
 import json
 from infrastructure.logging import get_logger
 from typing import List, Optional, Dict, Any
-from datetime import datetime
+from datetime import datetime, timezone
 
 import aiohttp
 
@@ -563,8 +563,8 @@ class GiteaProjectRepository(ProjectRepository):
     def _map_api_project_to_domain(self, api_data: Dict[str, Any]) -> Project:
         """Map Gitea API project data to domain Project object."""
         # For now, create a basic project since Gitea projects API might be limited
-        created_at = datetime.fromisoformat(api_data.get("created_at", datetime.utcnow().isoformat()).replace("Z", "+00:00"))
-        updated_at = datetime.fromisoformat(api_data.get("updated_at", datetime.utcnow().isoformat()).replace("Z", "+00:00"))
+        created_at = datetime.fromisoformat(api_data.get("created_at", datetime.now(timezone.utc).isoformat()).replace("Z", "+00:00"))
+        updated_at = datetime.fromisoformat(api_data.get("updated_at", datetime.now(timezone.utc).isoformat()).replace("Z", "+00:00"))
 
         return Project(
             id=str(api_data.get("id", 0)),