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/db.ts

@@ -65,6 +65,12 @@ async function applyMigrations(db: Client): Promise<void> {
       role           TEXT NOT NULL DEFAULT 'user',
       created_at     TEXT NOT NULL
     );
+
+    CREATE TABLE IF NOT EXISTS links (
+      key        TEXT PRIMARY KEY,
+      value      TEXT NOT NULL,
+      updated_at TEXT NOT NULL DEFAULT (datetime('now'))
+    );
   `)
 }