fix: harden week-two ordering, artwork and operations

app/core/limits.py

@@ -0,0 +1,13 @@
+"""Limits shared by upload admission and the malware scanner."""
+import os
+
+CLAMAV_STREAM_MAX_BYTES = 128 * 1024 * 1024  # infra/clamd.conf
+
+
+def scan_limit_bytes():
+    return min(CLAMAV_STREAM_MAX_BYTES, int(os.environ.get('SCAN_MAX_BYTES', '134217728')))
+
+
+def upload_limit_bytes():
+    transport = int(os.environ.get('MAX_UPLOAD_BYTES', '5368709120'))
+    return min(transport, scan_limit_bytes())