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/models/project_health.py

@@ -0,0 +1,51 @@
+from sqlalchemy import Column, String, Integer, DateTime, Enum, ForeignKey
+from sqlalchemy.orm import relationship
+from sqlalchemy.sql import func
+from app.core.database import Base
+import enum
+
+
+class RiskLevel(str, enum.Enum):
+    LOW = "low"
+    MEDIUM = "medium"
+    HIGH = "high"
+    CRITICAL = "critical"
+
+
+class ScheduleStatus(str, enum.Enum):
+    ON_TRACK = "on_track"
+    AT_RISK = "at_risk"
+    DELAYED = "delayed"
+
+
+class ResourceStatus(str, enum.Enum):
+    ADEQUATE = "adequate"
+    CONSTRAINED = "constrained"
+    OVERLOADED = "overloaded"
+
+
+class ProjectHealth(Base):
+    __tablename__ = "pjctrl_project_health"
+
+    id = Column(String(36), primary_key=True)
+    project_id = Column(String(36), ForeignKey("pjctrl_projects.id", ondelete="CASCADE"), nullable=False, unique=True)
+    health_score = Column(Integer, default=100, nullable=False)  # 0-100
+    risk_level = Column(
+        Enum("low", "medium", "high", "critical", name="risk_level_enum"),
+        default="low",
+        nullable=False
+    )
+    schedule_status = Column(
+        Enum("on_track", "at_risk", "delayed", name="schedule_status_enum"),
+        default="on_track",
+        nullable=False
+    )
+    resource_status = Column(
+        Enum("adequate", "constrained", "overloaded", name="resource_status_enum"),
+        default="adequate",
+        nullable=False
+    )
+    last_updated = Column(DateTime, server_default=func.now(), onupdate=func.now(), nullable=False)
+
+    # Relationships
+    project = relationship("Project", back_populates="health")