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>

frontend/src/components/ResourceHistory.tsx

@@ -41,11 +41,26 @@ export function ResourceHistory({ resourceType, resourceId, title = 'Change Hist
     return <div style={styles.empty}>No change history available</div>
   }
 
+  const handleKeyDown = (e: React.KeyboardEvent) => {
+    if (e.key === 'Enter' || e.key === ' ') {
+      e.preventDefault()
+      setExpanded(!expanded)
+    }
+  }
+
   return (
     <div style={styles.container}>
-      <div style={styles.header} onClick={() => setExpanded(!expanded)}>
+      <div
+        style={styles.header}
+        onClick={() => setExpanded(!expanded)}
+        role="button"
+        tabIndex={0}
+        onKeyDown={handleKeyDown}
+        aria-expanded={expanded}
+        aria-label={`${title}, ${logs.length} items`}
+      >
         <span style={styles.title}>{title}</span>
-        <span style={styles.toggleIcon}>{expanded ? '▼' : '▶'}</span>
+        <span style={styles.toggleIcon} aria-hidden="true">{expanded ? '▼' : '▶'}</span>
       </div>
       {expanded && (
         <div style={styles.content}>