Phase 11: remote UX & network attach (0.11.0)

- Live remote-stack logs over a WebSocket proxied through the central app to
  the agent (/ws/agent-logs/{agent}/{stack}); agent gains a WS log endpoint.
- Deploy to a remote host from the UI: host selector in the New Stack editor
  and template dialog; templates instantiate onto an agent via the proxy.
- Network attach/detach: expandable inspect view per network with
  connect/disconnect + container picker; GET /{id}/containers, POST connect/disconnect.
- Remove dead pages/Placeholder.tsx.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/components/stacks/LogViewer.tsx

@@ -21,7 +21,7 @@ function colorFor(service: string | null): string {
   return serviceColors[h % serviceColors.length];
 }
 
-export function LogViewer({ stackId }: { stackId: string }) {
+export function LogViewer({ stackId, agentId }: { stackId: string; agentId?: number }) {
   const [lines, setLines] = useState<{ service: string | null; line: string }[]>([]);
   const [autoScroll, setAutoScroll] = useState(true);
   const [connected, setConnected] = useState(false);
@@ -31,7 +31,11 @@ export function LogViewer({ stackId }: { stackId: string }) {
   useEffect(() => {
     if (!token) return;
     const proto = window.location.protocol === "https:" ? "wss" : "ws";
-    const url = `${proto}://${window.location.host}/ws/logs/${stackId}?token=${token}`;
+    const path =
+      agentId != null
+        ? `/ws/agent-logs/${agentId}/${stackId}`
+        : `/ws/logs/${stackId}`;
+    const url = `${proto}://${window.location.host}${path}?token=${token}`;
     const ws = new WebSocket(url);
     ws.onopen = () => setConnected(true);
     ws.onclose = () => setConnected(false);
@@ -49,7 +53,7 @@ export function LogViewer({ stackId }: { stackId: string }) {
       }
     };
     return () => ws.close();
-  }, [stackId, token]);
+  }, [stackId, agentId, token]);
 
   useEffect(() => {
     if (autoScroll && containerRef.current) {