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>

logs/run-20260107-212333/env.log

@@ -0,0 +1,18 @@
+Timestamp: 2026-01-07T13:23:35Z
+Python: Python 3.11.14
+Python Path: /Users/egg/miniconda3/envs/pjctrl/bin/python
+Node: v22.19.0
+NPM: 11.6.2
+Env file: /Users/egg/Projects/PROJECT CONTORL/backend/.env
+OK: MYSQL_HOST
+OK: MYSQL_PORT
+OK: MYSQL_USER
+OK: MYSQL_PASSWORD
+OK: MYSQL_DATABASE
+OK: REDIS_HOST
+OK: REDIS_PORT
+OK: JWT_SECRET_KEY
+OK: AUTH_API_URL
+OK: SYSTEM_ADMIN_EMAIL
+WARN: ENCRYPTION_MASTER_KEY not set
+MySQL: Port reachable (mysql.theaken.com:33306)