fix: batch signed log sync imports

docs/production-readiness-roadmap.md

@@ -130,6 +130,8 @@ it.
 - `[~]` Make multi-table writes transactional.
   Acceptance criteria:
   - `[x]` Signed operation and signature imports commit atomically.
+  - `[x]` Keychain/auth sync imports stage accepted records and commit accepted
+    op/signature groups through store batch transactions.
   - `[ ]` Multi-record sync imports cannot leave partial state after a local
     error.
   - `[x]` Tests cover failure injection for at least one multi-table path.