fix(update-center): cascade local and remote icon fallbacks

Keep update list icons from dropping straight to placeholders by retrying the remote store icon after local load failures. Align the update-center IPC and renderer types with the split local/remote icon contract.

src/global/typedefinition.ts

@@ -140,7 +140,8 @@ export interface UpdateCenterItem {
   currentVersion: string;
   newVersion: string;
   source: UpdateSource;
-  icon?: string;
+  localIcon?: string;
+  remoteIcon?: string;
   ignored?: boolean;
   downloadUrl?: string;
   fileName?: string;
@@ -156,7 +157,8 @@ export interface UpdateCenterTaskState {
   taskKey: string;
   packageName: string;
   source: UpdateSource;
-  icon?: string;
+  localIcon?: string;
+  remoteIcon?: string;
   status: UpdateCenterTaskStatus;
   progress: number;
   logs: Array<{ time: number; message: string }>;