🐛(backend) fix unescaped dot in regex pattern

The dot before (?P<extension>...) was not escaped and matched any
character instead of a literal period.

Escape it to align with MEDIA_STORAGE_URL_PATTERN, which correctly
uses \. for the file extension separator.

src/backend/core/enums.py

@@ -14,7 +14,7 @@ FILE_EXT_REGEX = r"[a-zA-Z0-9]{1,10}"
 
 # pylint: disable=line-too-long
 RECORDING_STORAGE_URL_PATTERN = re.compile(
-    f"{settings.MEDIA_URL:s}{settings.RECORDING_OUTPUT_FOLDER}/(?P<recording_id>{UUID_REGEX:s}).(?P<extension>{FILE_EXT_REGEX:s})"
+    f"{settings.MEDIA_URL:s}{settings.RECORDING_OUTPUT_FOLDER}/(?P<recording_id>{UUID_REGEX:s})\.(?P<extension>{FILE_EXT_REGEX:s})"
 )
 
 MEDIA_STORAGE_URL_PATTERN = re.compile(