Refactor job status handling to prevent race conditions

- Removed redundant error handling in handleListJobTasks.
- Introduced per-job mutexes in Manager to serialize updateJobStatusFromTasks calls, ensuring thread safety during concurrent task completions.
- Added methods to manage job status update mutexes, including creation and cleanup after job completion or failure.
- Improved error handling in handleGetJobStatusForRunner by consolidating error checks.

internal/manager/manager.go

@@ -89,6 +89,9 @@ type Manager struct {
 	// Throttling for task status updates (per task)
 	taskUpdateTimes   map[int64]time.Time // key: taskID
 	taskUpdateTimesMu sync.RWMutex
+	// Per-job mutexes to serialize updateJobStatusFromTasks calls and prevent race conditions
+	jobStatusUpdateMu   map[int64]*sync.Mutex // key: jobID
+	jobStatusUpdateMuMu sync.RWMutex
 
 	// Client WebSocket connections (new unified WebSocket)
 	// Key is "userID:connID" to support multiple tabs per user
@@ -162,6 +165,8 @@ func NewManager(db *database.DB, cfg *config.Config, auth *authpkg.Auth, storage
 		runnerJobConns:          make(map[string]*websocket.Conn),
 		runnerJobConnsWriteMu:   make(map[string]*sync.Mutex),
 		runnerJobConnsWriteMuMu: sync.RWMutex{}, // Initialize the new field
+		// Per-job mutexes for serializing status updates
+		jobStatusUpdateMu: make(map[int64]*sync.Mutex),
 	}
 
 	// Check for required external tools