code-to10 v6 A4: fix AuthStore.audit NameError (import sqlite3) + retry regression test

Pre-fix any first-attempt audit failure raised NameError at
auth.py:424 (sqlite3 never imported), aborting the 5-attempt
retry loop on attempt 1 and masking the original error. The
424-line coverage mystery is also explained: the only full-suite
hit is test_child_model.test_coordinator_inherits_child_defaults
via worker best-effort _audit swallowing an OperationalError
(database is locked); 422-423/426-427 stay uncovered because
rollback succeeds and NameError aborts before either raise.
Bubble audit (see report): no merge/release gate swallows the
NameError and proceeds, so this stays a downgrade, not a
production blocker.

(cherry picked from commit 039c6adbac3b120b5b9a1dcbafeff6a91407ce70)

cloud/auth.py

@@ -23,6 +23,7 @@ approve_merge -> maintainer，manage_project -> owner（仅 owner）。
 
 import hashlib
 import secrets
+import sqlite3
 from cloud.db import connect as _db_connect
 from cloud.ledger import append_entry as _ledger_append
 from cloud.ledger import ensure_schema as _ledger_ensure