fix: show empty state for unmanaged apps on Deployments tab

Previously showed an infinite spinner because unmanaged apps have no
PostgreSQL record. Now shows an "Unmanaged Application" message with
a link to create a managed app.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ui/src/pages/AppsTab/AppsTab.tsx

@@ -553,7 +553,19 @@ function AppDetailView({ appId: appSlug, environments, selectedEnv }: { appId: s
   const envMap = useMemo(() => new Map(environments.map((e) => [e.id, e])), [environments]);
   const sortedVersions = useMemo(() => [...versions].sort((a, b) => b.version - a.version), [versions]);
 
-  if (!app) return <PageLoader />;
+  if (!app) {
+    return (
+      <div style={{ padding: '40px 24px' }}>
+        <EmptyState
+          title="Unmanaged Application"
+          description={`"${appSlug}" is a discovered application registered by agents. To manage deployments, create it as a managed app first.`}
+        />
+        <div style={{ display: 'flex', justifyContent: 'center', marginTop: 16 }}>
+          <Button variant="primary" onClick={() => navigate('/apps/new')}>Create Managed App</Button>
+        </div>
+      </div>
+    );
+  }
 
   const env = envMap.get(app.environmentId);