Improve batch images and mask handling

Fixed batch image processing to prevent duplicates and layer deletion while ensuring proper mask loading from input_mask. Images are now added as new layers without removing existing ones, and masks are always checked from backend regardless of image state.

src/types.ts

@@ -94,6 +94,7 @@ export interface Canvas {
     inputDataLoaded: boolean;
     lastLoadedLinkId: any;
     lastLoadedMaskLinkId: any;
+    lastLoadedImageSrc?: string;
     outputAreaBounds: OutputAreaBounds;
     saveState: () => void;
     render: () => void;