feat: modernize web UI with dashboard and enhanced UX

- Add Lucide Icons library integration
- Implement metrics dashboard with 4 cards (users count, active, locked, version)
- Replace text-based user list with proper table including status badges
- Add toast notification system with slide-in animation
- Implement loading states with spinners for async operations
- Add action modal for user disable/enable operations
- Add status badges (success/warning/error/neutral) throughout
- Enhance CSS with hover effects, transitions, and modern styling
- Improve visual hierarchy with card-based layout
- Add icon-based actions for better UX

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

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

CHANGELOG.md

@@ -40,6 +40,7 @@ By: Codex (GPT-5)
 | 30.12.2025 | ⚙️ Code | ID: Update-API Endpunkte implementiert (GET /update/status, POST /update/check, POST /update/apply, POST /update/rollback, GET /update/logs). By: Claude Sonnet 4.5 |
 | 30.12.2025 | ⚙️ Code | ID: Update-UI im Web-Frontend implementiert (Status-Anzeige, Check/Apply/Rollback Buttons, Logs-Viewer). By: Claude Sonnet 4.5 |
 | 30.12.2025 | 🎨 UI | ID: Watchtower Theme implementiert (Sci-Fi Dark Mode mit Neon-Glow, bg-noise, CSS-Variables). By: Claude Sonnet 4.5 |
+| 30.12.2025 | 🎨 UI | ID: Web-UI modernisiert (Lucide Icons, Metrics Dashboard, User Table mit Badges, Toast Notifications, Loading States, Action Modals). By: Claude Sonnet 4.5 |
 
 ---
 ## Legende