feat: Dashboard redesign, plan permissions, and help docs improvements

Major updates including:
- Customizable dashboard with drag-and-drop widget grid layout
- Plan-based feature locking for plugins and tasks
- Comprehensive help documentation updates across all pages
- Plugin seeding in deployment process for all tenants
- Permission synchronization system for subscription plans
- QuotaOverageModal component and enhanced UX flows

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

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

frontend/src/pages/PluginMarketplace.tsx

@@ -29,6 +29,8 @@ import { Prism as SyntaxHighlighter } from 'react-syntax-highlighter';
 import { vscDarkPlus } from 'react-syntax-highlighter/dist/esm/styles/prism';
 import api from '../api/client';
 import { PluginTemplate, PluginCategory } from '../types';
+import { usePlanFeatures } from '../hooks/usePlanFeatures';
+import { LockedSection } from '../components/UpgradePrompt';
 
 // Category icon mapping
 const categoryIcons: Record<PluginCategory, React.ReactNode> = {
@@ -91,6 +93,11 @@ const PluginMarketplace: React.FC = () => {
   const [showWhatsNextModal, setShowWhatsNextModal] = useState(false);
   const [installedPluginId, setInstalledPluginId] = useState<string | null>(null);
 
+  // Check plan permissions
+  const { canUse, isLoading: permissionsLoading } = usePlanFeatures();
+  const hasPluginsFeature = canUse('plugins');
+  const isLocked = !hasPluginsFeature;
+
   // Fetch marketplace plugins
   const { data: plugins = [], isLoading, error } = useQuery<PluginTemplate[]>({
     queryKey: ['plugin-templates', 'marketplace'],
@@ -206,7 +213,7 @@ const PluginMarketplace: React.FC = () => {
     }
   };
 
-  if (isLoading) {
+  if (isLoading || permissionsLoading) {
     return (
       <div className="p-8">
         <div className="flex items-center justify-center h-64">
@@ -229,6 +236,7 @@ const PluginMarketplace: React.FC = () => {
   }
 
   return (
+    <LockedSection feature="plugins" isLocked={isLocked} variant="overlay">
     <div className="p-8 space-y-6 max-w-7xl mx-auto">
       {/* Header */}
       <div className="flex items-center justify-between">
@@ -702,6 +710,7 @@ const PluginMarketplace: React.FC = () => {
         </div>
       )}
     </div>
+    </LockedSection>
   );
 };