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/api/auth/router.py

@@ -1,53 +1,86 @@
-from fastapi import APIRouter, Depends, HTTPException, status
+from fastapi import APIRouter, Depends, HTTPException, status, Request
 from sqlalchemy.orm import Session
 
 from app.core.config import settings
 from app.core.database import get_db
 from app.core.security import create_access_token, create_token_payload
 from app.core.redis import get_redis
+from app.core.rate_limiter import limiter
 from app.models.user import User
+from app.models.audit_log import AuditAction
 from app.schemas.auth import LoginRequest, LoginResponse, UserInfo
 from app.services.auth_client import (
     verify_credentials,
     AuthAPIError,
     AuthAPIConnectionError,
 )
+from app.services.audit_service import AuditService
 from app.middleware.auth import get_current_user
 
 router = APIRouter()
 
 
 @router.post("/login", response_model=LoginResponse)
+@limiter.limit("5/minute")
 async def login(
-    request: LoginRequest,
+    request: Request,
+    login_request: LoginRequest,
     db: Session = Depends(get_db),
     redis_client=Depends(get_redis),
 ):
     """
     Authenticate user via external API and return JWT token.
     """
+    # Prepare metadata for audit logging
+    client_ip = request.client.host if request.client else "unknown"
+    user_agent = request.headers.get("user-agent", "unknown")
+
     try:
         # Verify credentials with external API
-        auth_result = await verify_credentials(request.email, request.password)
+        auth_result = await verify_credentials(login_request.email, login_request.password)
     except AuthAPIConnectionError:
+        # Log failed login attempt due to service unavailable
+        AuditService.log_event(
+            db=db,
+            event_type="user.login_failed",
+            resource_type="user",
+            action=AuditAction.LOGIN,
+            user_id=None,
+            resource_id=None,
+            changes={"email": login_request.email, "reason": "auth_service_unavailable"},
+            request_metadata={"ip_address": client_ip, "user_agent": user_agent},
+        )
+        db.commit()
         raise HTTPException(
             status_code=status.HTTP_503_SERVICE_UNAVAILABLE,
             detail="Authentication service temporarily unavailable",
         )
     except AuthAPIError as e:
+        # Log failed login attempt due to invalid credentials
+        AuditService.log_event(
+            db=db,
+            event_type="user.login_failed",
+            resource_type="user",
+            action=AuditAction.LOGIN,
+            user_id=None,
+            resource_id=None,
+            changes={"email": login_request.email, "reason": "invalid_credentials"},
+            request_metadata={"ip_address": client_ip, "user_agent": user_agent},
+        )
+        db.commit()
         raise HTTPException(
             status_code=status.HTTP_401_UNAUTHORIZED,
             detail="Invalid credentials",
         )
 
     # Find or create user in local database
-    user = db.query(User).filter(User.email == request.email).first()
+    user = db.query(User).filter(User.email == login_request.email).first()
 
     if not user:
         # Create new user based on auth API response
         user = User(
-            email=request.email,
-            name=auth_result.get("name", request.email.split("@")[0]),
+            email=login_request.email,
+            name=auth_result.get("name", login_request.email.split("@")[0]),
             is_active=True,
         )
         db.add(user)
@@ -82,6 +115,19 @@ async def login(
         access_token,
     )
 
+    # Log successful login
+    AuditService.log_event(
+        db=db,
+        event_type="user.login",
+        resource_type="user",
+        action=AuditAction.LOGIN,
+        user_id=user.id,
+        resource_id=user.id,
+        changes=None,
+        request_metadata={"ip_address": client_ip, "user_agent": user_agent},
+    )
+    db.commit()
+
     return LoginResponse(
         access_token=access_token,
         user=UserInfo(
@@ -106,7 +152,7 @@ async def logout(
     # Remove session from Redis
     redis_client.delete(f"session:{current_user.id}")
 
-    return {"message": "Successfully logged out"}
+    return {"detail": "Successfully logged out"}
 
 
 @router.get("/me", response_model=UserInfo)