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>

backend/services/network_service.py

@@ -86,6 +86,43 @@ def create_network(spec: dict) -> dict:
     return _summary(net)
 
 
+def connectable_containers(network_id: str) -> list[dict]:
+    """All containers on the host, flagged whether already on this network."""
+    client = get_client()
+    net = safe_call(client.networks.get, network_id)
+    net.reload()
+    connected = set((net.attrs.get("Containers") or {}).keys())
+    out = []
+    for c in safe_call(client.containers.list, all=True):
+        labels = c.labels or {}
+        out.append(
+            {
+                "id": c.id[:12],
+                "name": c.name,
+                "state": c.status,
+                "stack": labels.get(COMPOSE_PROJECT_LABEL),
+                "connected": c.id in connected,
+            }
+        )
+    return sorted(out, key=lambda x: x["name"])
+
+
+def connect_container(network_id: str, container: str, aliases: Optional[list[str]] = None) -> None:
+    if not (container or "").strip():
+        raise DockerError("invalid_request", "Container is required")
+    client = get_client()
+    net = safe_call(client.networks.get, network_id)
+    safe_call(net.connect, container, aliases=aliases or None)
+
+
+def disconnect_container(network_id: str, container: str, force: bool = False) -> None:
+    if not (container or "").strip():
+        raise DockerError("invalid_request", "Container is required")
+    client = get_client()
+    net = safe_call(client.networks.get, network_id)
+    safe_call(net.disconnect, container, force=force)
+
+
 def delete_network(network_id: str) -> None:
     client = get_client()
     net = safe_call(client.networks.get, network_id)