Add Security Dashboard application

Security Dashboard is a comprehensive security monitoring and management
dashboard for Cockpit.

Features:
- Real-time security monitoring
- System information dashboard
- Modern PatternFly UI
- Multi-language support

Repository: https://github.com/XintiWu/cockpit-SecurityGuard

Author: XintiWu

_data/applications.yml

@@ -291,3 +291,12 @@ package-manager:
   license: LGPL 2.1
   description: |
     DEB (APT) / RPM browsing and installation tool using PackageKit.
+
+security-dashboard:
+  title: Security Dashboard
+  package: cockpit-security-dashboard
+  source: https://github.com/XintiWu/cockpit-SecurityGuard
+  issues: https://github.com/XintiWu/cockpit-SecurityGuard/issues
+  license: LGPL 2.1
+  description: |
+    Security monitoring and management dashboard for Cockpit.