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>

domain/projects/services.py

@@ -5,7 +5,7 @@ Contains business logic for project-related operations.
 """
 
 from typing import Dict, Any, List
-from datetime import datetime, timedelta
+from datetime import datetime, timedelta, timezone
 from .models import Project, Milestone, ProjectState
 from .exceptions import ProjectValidationError
 
@@ -39,7 +39,7 @@ class ProjectManagementService:
     def calculate_project_velocity(self, project: Project, days_back: int = 30) -> float:
         """Calculate project velocity based on recent milestone completions."""
         completed_milestones = project.get_completed_milestones()
-        cutoff_date = datetime.utcnow() - timedelta(days=days_back)
+        cutoff_date = datetime.now(timezone.utc) - timedelta(days=days_back)
 
         # Count milestones completed in the specified period
         # Note: This would need milestone completion dates in a real implementation
@@ -132,7 +132,7 @@ class ProjectManagementService:
             )
 
         # Business rule: Due date cannot be in the past
-        if due_date and due_date < datetime.utcnow():
+        if due_date and due_date < datetime.now(timezone.utc):
             raise ProjectValidationError(
                 "Milestone due date cannot be in the past",
                 field="due_date",
@@ -148,7 +148,7 @@ class ProjectManagementService:
 
         # Higher priority for milestones with due dates
         if milestone.due_date:
-            days_until_due = (milestone.due_date - datetime.utcnow()).days
+            days_until_due = (milestone.due_date - datetime.now(timezone.utc)).days
             if days_until_due <= 7:
                 priority_score += 50  # Very urgent
             elif days_until_due <= 30: