feat: Implement comprehensive help system with contextual icons (#122)

* feat: implement comprehensive help system with contextual icons

- Add HelpModal component with navigation sidebar and 7 help sections
- Add HelpButton component for main header controls
- Add ContextualHelpIcon component for contextual help throughout UI
- Add help icons to all major UI sections:
  - Settings modals (Server Settings, General Settings)
  - Sync button with update system help
  - Tab headers (Available, Downloaded, Installed Scripts)
  - FilterBar and CategorySidebar
- Add comprehensive help content covering:
  - Server Settings: PVE server management, auth types, color coding
  - General Settings: Save filters, GitHub integration, authentication
  - Sync Button: Script metadata syncing explanation
  - Available Scripts: Browsing, filtering, downloading
  - Downloaded Scripts: Local script management and updates
  - Installed Scripts: Auto-detection feature (primary focus), manual management
  - Update System: Automatic/manual update process, release notes
- Improve VersionDisplay: remove 'Update Available' text, add 'Release Notes:' label
- Make help icons more noticeable with increased size
- Fix dark theme compatibility issues in help modal

* fix: resolve linting errors in HelpModal component

- Remove unused Filter import
- Fix unescaped entities by replacing apostrophes and quotes with HTML entities
- All linting errors resolved

* feat: implement release notes modal system

- Add getAllReleases API endpoint to fetch GitHub releases with notes
- Create ReleaseNotesModal component with localStorage version tracking
- Add sticky Footer component with release notes link
- Make version badge clickable to open release notes
- Auto-show modal after updates when version changes
- Track last seen version in localStorage to prevent repeated shows
- Highlight new version in modal when opened after update
- Add manual access via footer and version badge clicks

* fix: use nullish coalescing operator in ReleaseNotesModal

- Replace logical OR (||) with nullish coalescing (??) operator
- Fixes ESLint prefer-nullish-coalescing rule violation
- Ensures build passes successfully

src/app/_components/HelpButton.tsx

@@ -0,0 +1,40 @@
+'use client';
+
+import { useState } from 'react';
+import { HelpModal } from './HelpModal';
+import { Button } from './ui/button';
+import { HelpCircle } from 'lucide-react';
+
+interface HelpButtonProps {
+  initialSection?: string;
+}
+
+export function HelpButton({ initialSection }: HelpButtonProps) {
+  const [isOpen, setIsOpen] = useState(false);
+
+  return (
+    <>
+      <div className="flex flex-col sm:flex-row sm:items-center gap-3">
+        <div className="text-sm text-muted-foreground font-medium">
+          Need help? 
+        </div>
+        <Button
+          onClick={() => setIsOpen(true)}
+          variant="outline"
+          size="default"
+          className="inline-flex items-center"
+          title="Open Help"
+        >
+          <HelpCircle className="w-5 h-5 mr-2" />
+          Help
+        </Button>
+      </div>
+
+      <HelpModal 
+        isOpen={isOpen} 
+        onClose={() => setIsOpen(false)} 
+        initialSection={initialSection}
+      />
+    </>
+  );
+}