Reorganize admin nav by feature and soften light mode.

Sidebar lists one entry per feature; keep hub tabs only for sibling views (events, tickets, ranks/permissions, moderation, radio, analytics, devops). Soft cool-gray light canvas/surface replaces harsh white.

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

src/components/admin/admin-hub-chrome.tsx

@@ -30,7 +30,7 @@ export function AdminHubChrome({ children }: { children: ReactNode }) {
 			icon={hub.icon}
 			title={t(hub.titleKey)}
 			subtitle={t(hub.subtitleKey)}
-			tabs={<AdminSectionTabs tabs={tabs} />}
+			tabs={tabs.length > 1 ? <AdminSectionTabs tabs={tabs} /> : undefined}
 			className="admin-hub-panel"
 		>
 			{children}