🩹(backend) ignore non-recording uploads in storage webhook handler

With the introduction of background file uploads, a misconfigured
MinIO webhook could trigger the storage hook endpoint for unrelated
files.

While the dev setup now filters events via the MinIO lifecycle
configuration, add a safeguard at the application level.

Enforce a stricter filepath regex when parsing storage hook events
and ignore files outside the recording output directory.

Return a clean 200 response to acknowledge the webhook while
avoiding unnecessary processing.

src/backend/core/recording/event/parsers.py

@@ -88,7 +88,7 @@ class MinioParser:
 
         # pylint: disable=line-too-long
         self._filepath_regex = re.compile(
-            rf"(?P<url_encoded_folder_path>(?:[^%]+%2F)+)?(?P<recording_id>{UUID_REGEX})\.(?P<extension>{FILE_EXT_REGEX})"
+            rf"(?P<url_encoded_folder_path>(?:[^%]+%2F)+)?{settings.RECORDING_OUTPUT_FOLDER}%2F(?P<recording_id>{UUID_REGEX})\.(?P<extension>{FILE_EXT_REGEX})"
         )
 
     @staticmethod