feat: complete LOW priority code quality improvements

Backend:
- LOW-002: Add Query validation with max page size limits (100)
- LOW-003: Replace magic strings with TaskStatus.is_done flag
- LOW-004: Add 'creation' trigger type validation
- Add action_executor.py with UpdateFieldAction and AutoAssignAction

Frontend:
- LOW-005: Replace TypeScript 'any' with 'unknown' + type guards
- LOW-006: Add ConfirmModal component with A11Y support
- LOW-007: Add ToastContext for user feedback notifications
- LOW-009: Add Skeleton components (17 loading states replaced)
- LOW-010: Setup Vitest with 21 tests for ConfirmModal and Skeleton

Components updated:
- App.tsx, ProtectedRoute.tsx, Spaces.tsx, Projects.tsx, Tasks.tsx
- ProjectSettings.tsx, AuditPage.tsx, WorkloadPage.tsx, ProjectHealthPage.tsx
- Comments.tsx, AttachmentList.tsx, TriggerList.tsx, TaskDetailModal.tsx
- NotificationBell.tsx, BlockerDialog.tsx, CalendarView.tsx, WorkloadUserDetail.tsx

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

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

backend/app/api/reports/router.py

@@ -1,4 +1,4 @@
-from fastapi import APIRouter, Depends, HTTPException, status
+from fastapi import APIRouter, Depends, HTTPException, status, Query
 from sqlalchemy.orm import Session
 from typing import Optional
 
@@ -71,8 +71,8 @@ async def generate_weekly_report(
 
 @router.get("/api/reports/history", response_model=ReportHistoryListResponse)
 async def list_report_history(
-    limit: int = 10,
-    offset: int = 0,
+    limit: int = Query(10, ge=1, le=100, description="Number of reports to return"),
+    offset: int = Query(0, ge=0, description="Number of reports to skip"),
     db: Session = Depends(get_db),
     current_user: User = Depends(get_current_user),
 ):