Hold DNS cutover until play_state_sync succeeds on handback

Retries up to PLAY_SYNC_HANDBACK_RETRIES times (default 5, 60s apart)
before giving up — one successful run catches all state regardless of
outage length, so users land on current watch state after DNS flips.

Deployment/master.conf.template

@@ -686,6 +686,12 @@
     FALLBACK_PARTNERSHIP_SUSPEND_AFTER=120      # minutes without active partnership before suspending
                                                 # 0 = suspend immediately when partnership goes inactive
 
+# ━━━ Play State Sync — Handback ━━━
+# play_state_sync runs before DNS cutover so users land on current watch state.
+# Retried until success — DNS is held until sync completes or retries are exhausted.
+    PLAY_SYNC_HANDBACK_RETRIES=5        # attempts before giving up and proceeding to DNS cutover
+    PLAY_SYNC_HANDBACK_RETRY_DELAY=60   # seconds between retry attempts
+
 # ━━━ Failover Test ━━━
 # Controlled simulation of a failover event — run manually via fallback_test.sh.
     FALLBACK_TEST_BLOCK_WAIT=150    # seconds to wait after blocking connectivity