feat: implement automation module

- Event-based triggers (Phase 1):
  - Trigger/TriggerLog models with field_change type
  - TriggerService for condition evaluation and action execution
  - Trigger CRUD API endpoints
  - Task integration (status, assignee, priority changes)
  - Frontend: TriggerList, TriggerForm components

- Weekly reports (Phase 2):
  - ScheduledReport/ReportHistory models
  - ReportService for stats generation
  - APScheduler for Friday 16:00 job
  - Report preview/generate/history API
  - Frontend: WeeklyReportPreview, ReportHistory components

- Tests: 23 new tests (14 triggers + 9 reports)
- OpenSpec: add-automation change archived

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

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

backend/app/models/project.py

@@ -38,3 +38,4 @@ class Project(Base):
     department = relationship("Department", back_populates="projects")
     task_statuses = relationship("TaskStatus", back_populates="project", cascade="all, delete-orphan")
     tasks = relationship("Task", back_populates="project", cascade="all, delete-orphan")
+    triggers = relationship("Trigger", back_populates="project", cascade="all, delete-orphan")