feat(swarm): autonomous agent containers, Swarm Manager with auto-stop, /nodes UI overhaul

## 1. Fix /nodes Swarm Status Display
- Add SwarmStatusBanner component: clear green/red/loading state
- Shows nodeId, managerAddr, isManager badge
- Error state explains what to check (docker.sock mount)
- Header now shows 'swarm unreachable — check gateway' vs 'active'
- swarmOk now checks nodeId presence, not just data existence

## 2. Autonomous Agent Container
- New docker/Dockerfile.agent — builds Go agent binary from gateway/cmd/agent/
- New gateway/cmd/agent/main.go — standalone HTTP microservice:
  * GET /health — liveness probe with idle time info
  * POST /task — receives task, forwards to Gateway orchestrator
  * GET /info  — agent metadata (id, hostname, gateway url)
  * Idle watchdog: calls /api/swarm/agents/{name}/stop after IdleTimeoutMinutes
  * Connects to Swarm overlay network (goclaw-net) → reaches DB/Gateway by DNS
  * Env: AGENT_ID, GATEWAY_URL, DATABASE_URL, IDLE_TIMEOUT_MINUTES

## 3. Swarm Manager Agent (auto-stop after 15min idle)
- New gateway/internal/api/swarm_manager.go:
  * SwarmManager goroutine checks every 60s
  * Scales idle GoClaw agent services to 0 replicas after 15 min
  * Tracks lastActivity from task UpdatedAt timestamps
- New REST endpoints in gateway:
  * GET  /api/swarm/agents           — list agents with idleMinutes
  * POST /api/swarm/agents/{name}/start — scale up agent
  * POST /api/swarm/agents/{name}/stop  — scale to 0
  * DELETE /api/swarm/services/{id}     — remove service permanently
- SwarmManager started as background goroutine in main.go with context cancel

## 4. Docker Client Enhancements
- Added NetworkAttachment type and Networks field to ServiceSpec
- CreateAgentServiceFull(opts) — supports overlay networks, custom labels
- CreateAgentService() delegates to CreateAgentServiceFull for backward compat
- RemoveService(id) — DELETE /v1.44/services/{id}
- GetServiceLastActivity(id) — finds latest task UpdatedAt for idle detection

## 5. tRPC & Gateway Proxy
- New functions: removeSwarmService, listSwarmAgents, startSwarmAgent, stopSwarmAgent
- SwarmAgentInfo type with idleMinutes, lastActivity, desiredReplicas
- createAgentService now accepts networks[] parameter
- New tRPC endpoints: nodes.removeService, nodes.listAgents, nodes.startAgent, nodes.stopAgent

## 6. Nodes.tsx UI Overhaul
- SwarmStatusBanner component at top — no more silent 'connecting…'
- New 'Agents' tab with AgentManagerRow: idle time, auto-stop warning, start/stop/remove buttons
- IdleColor coding: green < 5m, yellow 5-10m, red 10m+ with countdown to auto-stop
- ServiceRow: added Remove button with confirmation dialog
- RemoveConfirmDialog component
- DeployAgentDialog: added overlay networks field, default env includes GATEWAY_URL
- All queries refetch after agent start/stop/remove

docker/Dockerfile.agent

@@ -0,0 +1,53 @@
+# ── GoClaw Agent Container ────────────────────────────────────────────────────
+#
+# Autonomous agent microservice that:
+#  1. Exposes a lightweight HTTP API (port 8080) for receiving tasks
+#  2. Has access to the Swarm overlay network (goclaw-net)
+#  3. Connects to the shared MySQL database for persistence
+#  4. Calls the LLM API via the GoClaw Gateway
+#  5. Auto-registers itself with the orchestrator on startup
+#
+# Build: docker build -f docker/Dockerfile.agent -t goclaw-agent:latest .
+# Deploy: docker service create --name goclaw-agent-NAME \
+#           --network goclaw-net \
+#           -e AGENT_ID=NAME \
+#           -e GATEWAY_URL=http://goclaw-gateway:18789 \
+#           -e DATABASE_URL=mysql://... \
+#           goclaw-agent:latest
+# ─────────────────────────────────────────────────────────────────────────────
+
+# ── Stage 1: Build Go agent binary ───────────────────────────────────────────
+FROM golang:1.23-alpine AS builder
+WORKDIR /src
+
+# Copy gateway module (agent reuses gateway internals)
+COPY gateway/go.mod gateway/go.sum ./
+RUN go mod download
+
+COPY gateway/ ./
+
+# Build the agent server binary
+RUN go build -o /agent-server ./cmd/agent/...
+
+# ── Stage 2: Runtime ──────────────────────────────────────────────────────────
+FROM alpine:3.20
+RUN apk add --no-cache ca-certificates curl wget tzdata
+
+WORKDIR /app
+COPY --from=builder /agent-server ./agent-server
+
+# Default environment (override at deploy time)
+ENV AGENT_ID=default-agent \
+    AGENT_PORT=8080 \
+    GATEWAY_URL=http://goclaw-gateway:18789 \
+    LLM_BASE_URL=https://ollama.com/v1 \
+    LLM_API_KEY="" \
+    DATABASE_URL="" \
+    IDLE_TIMEOUT_MINUTES=15
+
+EXPOSE 8080
+
+HEALTHCHECK --interval=15s --timeout=5s --start-period=10s --retries=3 \
+    CMD wget -qO- http://localhost:8080/health || exit 1
+
+ENTRYPOINT ["/app/agent-server"]