feat(backend): implement service monitor proto & connect it to http /agents

backend/internal/grpcsrv/collector/collector.go

@@ -186,3 +186,45 @@ func (c *Collector) Agents() []*Agent {
 	}
 	return result
 }
+
+// ServicesStream handles the ServicesUpdate client-streaming RPC.
+// Agents send service status updates which are stored in the collector.
+// Returns a single response when the agent closes the stream.
+func (c *Collector) ServicesStream(stream proto.Collector_ServicesStreamServer) error {
+	md, ok := metadata.FromIncomingContext(stream.Context())
+	if !ok {
+		return fmt.Errorf("no metadata in context")
+	}
+
+	whoamiVals := md["whoami"]
+	if len(whoamiVals) == 0 {
+		return fmt.Errorf("whoami metadata missing")
+	}
+	agentName := whoamiVals[0]
+
+	log.Printf("Agent %s started services update stream", agentName)
+
+	for {
+		update, err := stream.Recv()
+		if err == io.EOF {
+			log.Printf("Agent %s finished services update stream", agentName)
+			return stream.SendAndClose(&proto.ServicesUpdateResp{})
+		}
+		if err != nil {
+			return fmt.Errorf("failed to receive services update: %w", err)
+		}
+
+		c.mu.Lock()
+		if agent, ok := c.agents[agentName]; ok {
+			services := make([]string, 0, len(update.Services))
+			for _, s := range update.Services {
+				services = append(services, fmt.Sprintf("%s:%s", s.Name, s.Status))
+			}
+			agent.Services = services
+			log.Printf("Updated services for agent %s: %v", agentName, agent.Services)
+		} else {
+			log.Printf("Warning: received services update for unknown agent %s", agentName)
+		}
+		c.mu.Unlock()
+	}
+}