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/agent_app.py

@@ -16,7 +16,21 @@ from dataclasses import asdict
 
 import tempfile
 
-from fastapi import Depends, FastAPI, File, Form, Header, HTTPException, Query, Request, UploadFile
+import json
+
+from fastapi import (
+    Depends,
+    FastAPI,
+    File,
+    Form,
+    Header,
+    HTTPException,
+    Query,
+    Request,
+    UploadFile,
+    WebSocket,
+    WebSocketDisconnect,
+)
 from fastapi.responses import FileResponse, JSONResponse
 from pydantic import BaseModel
 
@@ -26,7 +40,7 @@ from services import backup_service, compose_service
 
 logger = logging.getLogger("stackpilot.agent")
 
-AGENT_VERSION = "0.10.0"
+AGENT_VERSION = "0.11.0"
 
 
 # --------------------------------------------------------------------------- #
@@ -274,6 +288,33 @@ async def restore_stack(
             os.unlink(tmp.name)
 
 
+@app.websocket("/agent/ws/logs/{stack_id}")
+async def ws_logs(websocket: WebSocket, stack_id: str, token: str | None = Query(default=None)):
+    """Stream `docker compose logs -f` to the central app (token via query param)."""
+    await websocket.accept()
+    expected = settings.AGENT_TOKEN
+    if not expected or token != expected:
+        await websocket.close(code=4401)
+        return
+    if not os.path.isdir(compose_service.stack_dir(stack_id)):
+        await websocket.send_text(json.dumps({"type": "error", "detail": "stack not found"}))
+        await websocket.close()
+        return
+    args = ["logs", "--no-color", "--tail", "200", "--timestamps", "-f"]
+    try:
+        async for line in compose_service.stream_compose(stack_id, args):
+            await websocket.send_text(
+                json.dumps({"type": "log", "stack_id": stack_id, "service": None, "line": line})
+            )
+    except WebSocketDisconnect:
+        pass
+    except Exception as exc:  # noqa: BLE001
+        try:
+            await websocket.send_text(json.dumps({"type": "error", "detail": str(exc)}))
+        except Exception:  # noqa: BLE001
+            pass
+
+
 @app.get("/agent/health")
 def health() -> dict:
     return {"status": "ok"}