feat: add s3_exists to DataStore

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/vl_apify_shared/data_store.py

@@ -3,6 +3,7 @@ import csv
 import io
 import json
 import boto3
+from botocore.exceptions import ClientError
 from dataclasses import dataclass
 from typing import Any
 import hashlib
@@ -87,5 +88,16 @@ class DataStore:
             Metadata=metadata,
         )
 
+    async def s3_exists(self, key: str) -> bool:
+        def _check():
+            try:
+                self._client.head_object(Bucket=self.config.bucket, Key=key)
+                return True
+            except ClientError as e:
+                if e.response["Error"]["Code"] == "404":
+                    return False
+                raise
+        return await asyncio.to_thread(_check)
+
     def hash(self, content: str):
         return hashlib.md5(content.encode()).hexdigest()