feat: add top tab bar to Instance settings panel

Renders tab pills (General, Streaming, Storage, Users) at the
top of the content area, matching Discord's Family Center pattern.
Works alongside the sidebar sub-links — both navigate the same tabs.

packages/web/src/components/modals/settingsPanels/InstancePanel.tsx

@@ -34,8 +34,24 @@ export function InstancePanel() {
     fetchStreamingLimits();
   }, [fetchInstanceSettings, fetchStreamingLimits]);
 
+  const tabPillClass = (t: SubTab) =>
+    `px-3 py-1.5 text-sm rounded-md transition-colors ${
+      subTab === t
+        ? 'text-txt-primary font-medium border-b-2 border-accent-primary'
+        : 'text-txt-tertiary hover:text-txt-secondary'
+    }`;
+
   return (
     <div className="space-y-4">
+      {/* Top tab bar */}
+      <div className="flex gap-1 border-b border-white/[0.04] pb-0">
+        {SECTIONS.map((s) => (
+          <button key={s.id} onClick={() => setSubTab(s.id as SubTab)} className={tabPillClass(s.id as SubTab)}>
+            {s.label}
+          </button>
+        ))}
+      </div>
+
       {subTab === 'general' && <GeneralPanel />}
       {subTab === 'streaming' && <StreamingPanel />}
       {subTab === 'storage' && <StoragePanel />}