fix: improve image extension handling and error reporting in upload functions

mobile/src/pages/datacards.tsx

@@ -776,7 +776,7 @@ function ImageRotatorFields({ form, onChange, onUrlsChange }: ImageRotatorFields
     if (result.canceled) return;
     const asset = result.assets[0];
     if (!asset.base64) { Alert.alert("Error", "Could not read image data."); return; }
-    const ext = asset.uri.split(".").pop()?.toLowerCase() ?? "jpg";
+    const ext = (asset.mimeType?.split("/")[1] ?? asset.uri.split(".").pop() ?? "jpg").toLowerCase();
     setUploading(true);
     try {
       const res = await fetch(`${BASE_URL}/push_upload_images`, {