chore: server-changes note for snapshots-since replica fallback

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: d-cs

.server-changes/snapshots-since-replica-primary-fallback.md

@@ -0,0 +1,8 @@
+---
+area: webapp
+type: improvement
+---
+
+Run snapshot polling no longer errors or pays extra latency when the database read replica
+briefly lags behind the primary (`RUN_ENGINE_READ_REPLICA_SNAPSHOTS_SINCE_ENABLED`): the read
+is served from the primary instead.