feat: auto-detect podman/docker in agent, add studentId to activation response, fix download URLs

agent/websocket.go

@@ -15,6 +15,7 @@ type WSMessage struct {
 	Type          string `json:"type,omitempty"`
 	Port          int    `json:"port,omitempty"`
 	ComposeConfig string `json:"composeConfig,omitempty"`
+	StudentId     string `json:"studentId,omitempty"`
 	StudentName   string `json:"studentName,omitempty"`
 	Error         string `json:"error,omitempty"`
 }
@@ -84,7 +85,7 @@ func handleMessage(conn *websocket.Conn, msg WSMessage, dataDir, nodeID string)
 	case "activate":
 		// handled by UI, but server can also push activation response
 		if msg.StudentName != "" {
-			act := &Activation{Activated: true, StudentName: msg.StudentName, Code: msg.Code}
+			act := &Activation{Activated: true, StudentId: msg.StudentId, StudentName: msg.StudentName, Code: msg.Code}
 			saveActivation(dataDir, act)
 			log.Printf("Activated as %s", msg.StudentName)
 		}