fix: save dominant color from image upload to item record

ImageUpload was discarding the dominantColor returned by the upload
API. Now it passes the color through onChange and the item detail
page saves it to the item record immediately after upload.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/client/components/ImageUpload.tsx

@@ -7,7 +7,7 @@ interface ImageUploadProps {
 	value: string | null;
 	imageUrl?: string | null;
 	dominantColor?: string | null;
-	onChange: (filename: string | null) => void;
+	onChange: (filename: string | null, dominantColor?: string | null) => void;
 	onCropChange?: (crop: { zoom: number; x: number; y: number }) => void;
 }
 
@@ -49,8 +49,11 @@ export function ImageUpload({
 
 		setUploading(true);
 		try {
-			const result = await apiUpload<{ filename: string }>("/api/images", file);
-			onChange(result.filename);
+			const result = await apiUpload<{
+				filename: string;
+				dominantColor?: string | null;
+			}>("/api/images", file);
+			onChange(result.filename, result.dominantColor);
 			if (onCropChange) {
 				setShowCropEditor(true);
 			}

src/client/routes/items/$itemId.tsx

@@ -274,9 +274,15 @@ function ItemDetail() {
 						value={form.imageFilename}
 						imageUrl={imageUrl}
 						dominantColor={item.dominantColor}
-						onChange={(filename) =>
-							setForm((f) => ({ ...f, imageFilename: filename }))
-						}
+						onChange={(filename, dominantColor) => {
+							setForm((f) => ({ ...f, imageFilename: filename }));
+							if (dominantColor) {
+								updateItem.mutate({
+									id: item.id,
+									dominantColor,
+								});
+							}
+						}}
 						onCropChange={(crop) => {
 							updateItem.mutate({
 								id: item.id,