feat: complete issue fixes and implement remaining features

## Critical Issues (CRIT-001~003) - All Fixed
- JWT secret key validation with pydantic field_validator
- Login audit logging for success/failure attempts
- Frontend API path prefix removal

## High Priority Issues (HIGH-001~008) - All Fixed
- Project soft delete using is_active flag
- Redis session token bytes handling
- Rate limiting with slowapi (5 req/min for login)
- Attachment API permission checks
- Kanban view with drag-and-drop
- Workload heatmap UI (WorkloadPage, WorkloadHeatmap)
- TaskDetailModal integrating Comments/Attachments
- UserSelect component for task assignment

## Medium Priority Issues (MED-001~012) - All Fixed
- MED-001~005: DB commits, N+1 queries, datetime, error format, blocker flag
- MED-006: Project health dashboard (HealthService, ProjectHealthPage)
- MED-007: Capacity update API (PUT /api/users/{id}/capacity)
- MED-008: Schedule triggers (cron parsing, deadline reminders)
- MED-009: Watermark feature (image/PDF watermarking)
- MED-010~012: useEffect deps, DOM operations, PDF export

## New Files
- backend/app/api/health/ - Project health API
- backend/app/services/health_service.py
- backend/app/services/trigger_scheduler.py
- backend/app/services/watermark_service.py
- backend/app/core/rate_limiter.py
- frontend/src/pages/ProjectHealthPage.tsx
- frontend/src/components/ProjectHealthCard.tsx
- frontend/src/components/KanbanBoard.tsx
- frontend/src/components/WorkloadHeatmap.tsx

## Tests
- 113 new tests passing (health: 32, users: 14, triggers: 35, watermark: 32)

## OpenSpec Archives
- add-project-health-dashboard
- add-capacity-update-api
- add-schedule-triggers
- add-watermark-feature
- add-rate-limiting
- enhance-frontend-ux
- add-resource-management-ui

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/app/services/report_service.py

@@ -1,5 +1,5 @@
 import uuid
-from datetime import datetime, timedelta
+from datetime import datetime, timedelta, timezone
 from typing import Dict, Any, List, Optional
 from sqlalchemy.orm import Session
 from sqlalchemy import func
@@ -15,9 +15,15 @@ class ReportService:
 
     @staticmethod
     def get_week_start(date: Optional[datetime] = None) -> datetime:
-        """Get the start of the week (Monday) for a given date."""
+        """Get the start of the week (Monday) for a given date.
+
+        Returns a naive datetime for compatibility with database values.
+        """
         if date is None:
-            date = datetime.utcnow()
+            date = datetime.now(timezone.utc).replace(tzinfo=None)
+        elif date.tzinfo is not None:
+            # Convert to naive datetime for consistency
+            date = date.replace(tzinfo=None)
         # Get Monday of the current week
         days_since_monday = date.weekday()
         week_start = date - timedelta(days=days_since_monday)
@@ -37,7 +43,8 @@ class ReportService:
         week_end = week_start + timedelta(days=7)
         next_week_start = week_end
         next_week_end = next_week_start + timedelta(days=7)
-        now = datetime.utcnow()
+        # Use naive datetime for comparison with database values
+        now = datetime.now(timezone.utc).replace(tzinfo=None)
 
         # Get projects owned by the user
         projects = db.query(Project).filter(Project.owner_id == user_id).all()
@@ -189,7 +196,7 @@ class ReportService:
         return {
             "week_start": week_start.isoformat(),
             "week_end": week_end.isoformat(),
-            "generated_at": datetime.utcnow().isoformat(),
+            "generated_at": datetime.now(timezone.utc).replace(tzinfo=None).isoformat(),
             "projects": project_details,
             "summary": {
                 "completed_count": len(completed_tasks),
@@ -235,7 +242,8 @@ class ReportService:
         db.add(report_history)
 
         # Update last_sent_at
-        scheduled_report.last_sent_at = datetime.utcnow()
+        # Use naive datetime for consistency with database storage
+        scheduled_report.last_sent_at = datetime.now(timezone.utc).replace(tzinfo=None)
 
         db.commit()
 
@@ -304,7 +312,8 @@ class ReportService:
                 db.add(history)
 
                 # Update last_sent_at
-                scheduled_report.last_sent_at = datetime.utcnow()
+                # Use naive datetime for consistency with database storage
+                scheduled_report.last_sent_at = datetime.now(timezone.utc).replace(tzinfo=None)
 
                 # Send notification
                 ReportService.send_report_notification(db, scheduled_report.recipient_id, content)