fix(server): explicitly capture 8 characters for dash-less ISO 8601

This should make it harder to submit an invalid date. All dates must be
in ISO 8601 format without the dashes, like 20231130.

server/config/settings.py

@@ -278,7 +278,7 @@
     ),
     "SHIPPER_FILE_NAME_FORMAT": (
         "[A-Za-z]+-(?P<version>[a-z0-9.]+)-(?P<codename>[A-Za-z0-9_]+)-OFFICIAL-("
-        "?P<variant>[a-z]+)-(?P<date>[0-9]+).zip",
+        "?P<variant>[a-z]+)-(?P<date>[0-9]{8}).zip",
         "Regex pattern to use when parsing file names of uploaded artifacts. The "
         "pattern must include the following four named match groups; otherwise an "
         "exception will occur during uploading: `version', `codename`, `variant`, "