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/logging/formatters.py

@@ -8,7 +8,7 @@ with context-aware logging capabilities.
 import json
 import logging
 import traceback
-from datetime import datetime
+from datetime import datetime, timezone
 from typing import Dict, Any, Optional
 
 from .context import get_current_log_context
@@ -54,7 +54,7 @@ class BaseFormatter(logging.Formatter):
 
     def _add_standard_fields(self, record: logging.LogRecord) -> None:
         """Add standard fields to log record."""
-        record.timestamp = datetime.utcnow().isoformat() + 'Z'
+        record.timestamp = datetime.now(timezone.utc).isoformat() + 'Z'
         record.logger_name = record.name
         record.level_name = record.levelname
         record.thread_name = record.threadName