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/Footer.tsx

@@ -0,0 +1,64 @@
+'use client';
+
+import { api } from '~/trpc/react';
+import { Button } from './ui/button';
+import { ExternalLink, FileText } from 'lucide-react';
+
+interface FooterProps {
+  onOpenReleaseNotes: () => void;
+}
+
+export function Footer({ onOpenReleaseNotes }: FooterProps) {
+  const { data: versionData } = api.version.getCurrentVersion.useQuery();
+
+  return (
+    <footer className="sticky bottom-0 mt-auto border-t border-border bg-muted/30 py-6 backdrop-blur-sm">
+      <div className="container mx-auto px-4">
+        <div className="flex flex-col sm:flex-row items-center justify-between gap-4 text-sm text-muted-foreground">
+          <div className="flex items-center gap-4">
+            <span>© 2024 PVE Scripts Local</span>
+            {versionData?.success && versionData.version && (
+              <Button
+                variant="ghost"
+                size="sm"
+                onClick={onOpenReleaseNotes}
+                className="h-auto p-1 text-xs hover:text-foreground"
+              >
+                v{versionData.version}
+              </Button>
+            )}
+          </div>
+          
+          <div className="flex items-center gap-4">
+            <Button
+              variant="ghost"
+              size="sm"
+              onClick={onOpenReleaseNotes}
+              className="h-auto p-2 text-xs hover:text-foreground"
+            >
+              <FileText className="h-3 w-3 mr-1" />
+              Release Notes
+            </Button>
+            
+            <Button
+              variant="ghost"
+              size="sm"
+              asChild
+              className="h-auto p-2 text-xs hover:text-foreground"
+            >
+              <a
+                href="https://github.com/community-scripts/ProxmoxVE-Local"
+                target="_blank"
+                rel="noopener noreferrer"
+                className="flex items-center gap-1"
+              >
+                <ExternalLink className="h-3 w-3" />
+                GitHub
+              </a>
+            </Button>
+          </div>
+        </div>
+      </div>
+    </footer>
+  );
+}