feat: add admin links management and updaterup page

- Implemented AdminLinksPage for managing link entries with admin role check.
- Created API routes for fetching, updating, and deleting link entries.
- Added ProductTabs component for navigation between Backerup and Updaterup.
- Developed UpdaterupPage with detailed features, setup instructions, and statistics.
- Introduced links database functionality for runtime-editable link overrides.

frontend/lib/links.ts

@@ -26,6 +26,12 @@ export const LINKS = {
   dockerImage:        "gitea.doomlabs.de/kptltd00m/backerup:latest",
   /** Default UI port the container exposes */
   uiPort:             "8080",
+
+  // ── Updaterup ─────────────────────────────────────────────
+  /** Updaterup repository root */
+  updaterupGitea:     "https://gitea.doomlabs.de/KptltD00M/updaterup",
+  /** Updaterup Docker image reference */
+  updaterupDockerImage: "gitea.doomlabs.de/kptltd00m/updaterup:latest",
 } as const;
 
 export type Links = typeof LINKS;