rename appdata-Failover→appdata-Fallback in docs; critical sync 15→30min; transcode 3→7min

appdata-Failover → appdata-Fallback:
  All .md files updated — scripts and confs already used appdata-Fallback.
  Share was renamed; docs were the only stale references.

critical_sync_maintenance.sh: */15 → */30, 96/day → 48/day:
  critical_sync_maintenance.sh header, master.conf, host1/2.conf comments,
  Orchestrators README, User Script Plug-in README, Partnership README/manual/script,
  Docker_Essentials README/downloaders_reset.sh, Fallback README,
  weekly_sync_maintenance.sh, user_script_plug-in.sh all updated.

rsync_emby_failover User Script superseded:
  Emby dirty sync was already in HOST1_CRITICAL_SYNC_SHARES — it now runs inside
  critical_sync_maintenance.sh every 30min alongside auth sync and partnership check.
  Section in User Script Plug-in README marked for deletion from plugin.

transcode_management.sh: */3 → */7:
  transcode_management.sh, transcode_manager.sh, transcode_cleanup.sh headers,
  Transcodes README/manual, Orchestrators README, User Script Plug-in README,
  user_script_plug-in.sh all updated.

Fallback/README-Fallback.md

@@ -102,7 +102,7 @@ know the full library — arr_sync kept them in union while both servers were on
 
 NPM, LLDAP, and Authelia run actively on both servers at all times. HOST2 needs them running
 to serve his own users daily — this is not a fallback-only configuration. HOST1 is source of
-truth: all changes mirror to HOST2 every 15 minutes via critical sync.
+truth: all changes mirror to HOST2 every 30 minutes via critical sync.
 
 When DNS cuts over, auth is already running on the covering server. The 30-60 second dead
 zone where auth is coming up after DNS has already switched does not exist.