iOS thumbnails: add batch-thumbs command for future optimization

batch-thumbs pulls multiple files in one Python process session,
amortising the pymobiledevice3 startup cost. Not yet wired into the
app — thumbnails load lazily per-cell and cache permanently.

Known limitation: first load of iPhone thumbnails is slow (~2-3s each)
because each pull spawns a new Python process. After first view they
are instant from the on-disk cache.

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

@@ -157,6 +157,37 @@ async def cmd_pull_thumb(device_path: str, local_path: str):
         sys.exit(1)
 
 
+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.
+    """
+    try:
+        pairs = json.loads(pairs_json)
+        lockdown = await get_lockdown()
+        afc = await get_afc(lockdown)
+        results = []
+        for device_path, local_path in pairs:
+            try:
+                os.makedirs(os.path.dirname(os.path.abspath(local_path)), exist_ok=True)
+                try:
+                    data = await afc.fread(device_path, 512 * 1024, 0)
+                except Exception:
+                    await afc.pull(device_path, local_path)
+                    results.append({'devicePath': device_path, 'ok': True})
+                    continue
+                with open(local_path, 'wb') as f:
+                    f.write(data)
+                results.append({'devicePath': device_path, 'ok': True})
+            except Exception as e:
+                results.append({'devicePath': device_path, 'ok': False, 'error': str(e)})
+        print(json.dumps(results))
+    except Exception as e:
+        print(f'Error: {e}', file=sys.stderr)
+        sys.exit(1)
+
+
 async def cmd_delete(device_path: str):
     try:
         lockdown = await get_lockdown()
@@ -183,6 +214,8 @@ if __name__ == '__main__':
         asyncio.run(cmd_pull(sys.argv[2], sys.argv[3]))
     elif command == 'pull-thumb' and len(sys.argv) == 4:
         asyncio.run(cmd_pull_thumb(sys.argv[2], sys.argv[3]))
+    elif command == 'batch-thumbs' and len(sys.argv) == 3:
+        asyncio.run(cmd_batch_thumbs(sys.argv[2]))
     elif command == 'delete' and len(sys.argv) == 3:
         asyncio.run(cmd_delete(sys.argv[2]))
     else: