feat: implement Agent Presence Indicators (MVP)

Backend:
- Add /api/v1/agents/presence endpoint
- Integrate with matrix-presence-aggregator
- Add DAGI router health checks

Frontend:
- Create useAgentPresence hook
- Create AgentPresenceBadge component
- Integrate into /agents list page
- Integrate into /agents/:agentId cabinet

Shows real-time online/offline status for all agents.

services/city-service/routes_city.py

@@ -1407,6 +1407,115 @@ async def get_microdao_chat_room(slug: str):
         raise HTTPException(status_code=500, detail="Failed to get microdao chat room")
 
 
+# =============================================================================
+# Presence API (TASK_PHASE_AGENT_PRESENCE_INDICATORS_MVP)
+# =============================================================================
+
+@api_router.get("/agents/presence")
+async def get_agents_presence():
+    """
+    Отримати presence статус всіх активних агентів.
+    Повертає Matrix presence + DAGI router health.
+    """
+    try:
+        # Get all agents from DB
+        agents = await repo_city.list_agents_summaries(limit=1000)
+
+        # Get Matrix presence from matrix-presence-aggregator
+        matrix_presence = await get_matrix_presence_status()
+
+        # Get DAGI router health (simplified for MVP)
+        dagi_health = await get_dagi_router_health()
+
+        # Combine presence data
+        presence_data = []
+        for agent in agents:
+            agent_id = agent["id"]
+            node_id = agent.get("node_id")
+
+            # Matrix presence
+            matrix_status = matrix_presence.get(agent_id, {}).get("status", "offline")
+            last_seen = matrix_presence.get(agent_id, {}).get("last_seen")
+
+            # DAGI router presence (node-level)
+            dagi_status = "unknown"
+            if node_id and node_id in dagi_health:
+                dagi_status = dagi_health[node_id].get("router_status", "unknown")
+
+            presence_data.append({
+                "agent_id": agent_id,
+                "display_name": agent.get("display_name", agent_id),
+                "matrix_presence": matrix_status,
+                "dagi_router_presence": dagi_status,
+                "last_seen": last_seen,
+                "node_id": node_id
+            })
+
+        return {"presence": presence_data}
+
+    except Exception as e:
+        logger.error(f"Failed to get agents presence: {e}")
+        raise HTTPException(status_code=500, detail="Failed to get agents presence")
+
+
+async def get_matrix_presence_status():
+    """
+    Get Matrix presence from matrix-presence-aggregator.
+    Returns dict: agent_id -> {status: 'online'|'unavailable'|'offline', last_seen: timestamp}
+    """
+    try:
+        async with httpx.AsyncClient(timeout=5.0) as client:
+            response = await client.get("http://matrix-presence-aggregator:8080/api/presence/agents")
+            if response.status_code == 200:
+                data = response.json()
+                return data.get("agents", {})
+            else:
+                logger.warning(f"Matrix presence aggregator returned {response.status_code}")
+                return {}
+    except Exception as e:
+        logger.warning(f"Failed to get Matrix presence: {e}")
+        return {}
+
+
+async def get_dagi_router_health():
+    """
+    Get DAGI router health from node-registry or direct ping.
+    Returns dict: node_id -> {router_status: 'healthy'|'degraded'|'offline'}
+    """
+    try:
+        # Try to get from node-registry first
+        async with httpx.AsyncClient(timeout=5.0) as client:
+            response = await client.get("http://dagi-node-registry:9205/api/v1/health")
+            if response.status_code == 200:
+                data = response.json()
+                return data.get("nodes", {})
+            else:
+                logger.warning(f"Node registry returned {response.status_code}")
+    except Exception as e:
+        logger.warning(f"Failed to get DAGI router health from node-registry: {e}")
+
+    # Fallback: try direct ping to known nodes
+    try:
+        known_nodes = ["node-1-hetzner-gex44", "node-2-macbook-m4max"]
+        health_data = {}
+
+        for node_id in known_nodes:
+            try:
+                async with httpx.AsyncClient(timeout=2.0) as client:
+                    response = await client.get(f"http://dagi-router-{node_id}:8080/health")
+                    if response.status_code == 200:
+                        health_data[node_id] = {"router_status": "healthy"}
+                    else:
+                        health_data[node_id] = {"router_status": "degraded"}
+            except Exception:
+                health_data[node_id] = {"router_status": "offline"}
+
+        return health_data
+    except Exception as e:
+        logger.warning(f"Failed to get DAGI router health: {e}")
+        return {}
+
+
 # =============================================================================
 # City Feed API
 # =============================================================================