client: improve error message on failed upload

Changelog: Fixed
Ref: https://github.com/misskey-dev/misskey/issues/8574

locales/en-US.yml

@@ -233,6 +233,9 @@ resetAreYouSure: "Really reset?"
 saved: "Saved"
 messaging: "Chat"
 upload: "Upload"
+uploadFailed: "Upload failed"
+uploadFailedDescription: "The file could not be uploaded."
+uploadFailedSize: "The file is too large to be uploaded."
 keepOriginalUploading: "Keep original image"
 keepOriginalUploadingDescription: "Saves the originally uploaded image as-is. If turned\
   \ off, a version to display on the web will be generated on upload."

packages/client/src/scripts/upload.ts

@@ -83,10 +83,18 @@ export function uploadFile(
 					// TODO: 消すのではなくて再送できるようにしたい
 					uploads.value = uploads.value.filter(x => x.id !== id);
 
+					let text = i18n.ts.uploadFailedDescription;
+					if (xhr.status == 413) {
+						// the file was too large
+						text = i18n.ts.uploadFailedSize;
+					} else if (xhr.response?.error?.message != null) {
+						text = xhr.response?.error?.message;
+					}
+
 					alert({
 						type: 'error',
-						title: 'Failed to upload',
+						title: i18n.ts.uploadFailed,
-						text: `${JSON.stringify(ev.target?.response)}, ${JSON.stringify(xhr.response)}`,
+						text,
 					});
 
 					reject();