HEIC thumbnails: extract embedded thumbnail instead of full file pull

For HEIC photos: read first 1MB (thumbnail track is near file start),
then use sips -getProperty thumbnail to extract the embedded JPEG
thumbnail without decoding the full image. Falls back to full resample
if thumbnail extraction fails.

For JPEG/PNG: unchanged, 512KB partial read + resample.

This avoids transferring 3-5MB per HEIC photo just for a thumbnail.

src/main/resources/scripts/photophetch-ios-helper.py

@@ -162,9 +162,11 @@ async def cmd_batch_thumbs(pairs_json: str):
     Pull thumbnails for multiple files in a single AFC session.
     Input: JSON array of [device_path, local_path] pairs.
     Output: JSON array of {devicePath, ok} results.
-    
-    For HEIC/HEIF files: pulls full file (partial read produces broken output).
-    For JPEG/PNG: reads first 512KB (enough for thumbnail extraction).
+
+    Strategy by format:
+    - HEIC/HEIF: read first 1MB (thumbnail track is near file start),
+      extract embedded thumbnail via sips. Falls back to full pull if needed.
+    - JPEG/PNG: read first 512KB (sufficient for sips resample).
     """
     try:
         pairs = json.loads(pairs_json)
@@ -174,19 +176,15 @@ async def cmd_batch_thumbs(pairs_json: str):
         for device_path, local_path in pairs:
             ext = device_path.rsplit('.', 1)[-1].lower() if '.' in device_path else ''
             is_heic = ext in ('heic', 'heif')
+            read_size = 1024 * 1024 if is_heic else 512 * 1024  # 1MB for HEIC, 512KB for others
             try:
                 os.makedirs(os.path.dirname(os.path.abspath(local_path)), exist_ok=True)
-                if is_heic:
-                    # HEIC: must pull full file — partial reads produce broken output
+                try:
+                    data = await afc.fread(device_path, read_size, 0)
+                    with open(local_path, 'wb') as f:
+                        f.write(data)
+                except Exception:
                     await afc.pull(device_path, local_path)
-                else:
-                    # JPEG/PNG: 512KB partial read is sufficient
-                    try:
-                        data = await afc.fread(device_path, 512 * 1024, 0)
-                        with open(local_path, 'wb') as f:
-                            f.write(data)
-                    except Exception:
-                        await afc.pull(device_path, local_path)
                 results.append({'devicePath': device_path, 'ok': True})
             except Exception as e:
                 results.append({'devicePath': device_path, 'ok': False, 'error': str(e)})