Reorganize admin into tabbed hubs with a condensed sidebar.

Replace the long flat nav with hub entries, shared AdminHubChrome tabs, and AdminPageShell. Existing URLs stay stable; Settings/Radio and other sections now share one chrome.

Co-authored-by: Cursor <[email protected]>

src/app/globals.css

@@ -505,6 +505,12 @@ tbody tr:hover {
 	scroll-margin-top: 1rem;
 }
 
+/* Hub chrome already shows the section title — soften page-level heroes. */
+.admin-hub-panel > .space-y-6 > div:first-child > h1.text-3xl {
+	font-size: 1.15rem;
+	letter-spacing: -0.01em;
+}
+
 /* Page heading */
 .admin-page main > h1:first-child,
 .admin-page > h1:first-child {