fix Failover→Fallback naming and missing/stale script references

Failover/ was renamed to Fallback/ — all script paths and README links
updated across README.md, Orchestrators README, and User Script Plug-in README.

array_start.sh → array_started.sh in Orchestrators scripts table (wrong name).

fallback_state_reset.sh: script is referenced in User Script Plug-in README
but does not exist in Fallback/. Entry updated to document it as not yet built
and provides the manual workaround (direct state file write).

Note: /mnt/user/appdata-Failover/ share path references left unchanged —
that is the actual unRAID share name on the server, not the script folder.

README.md

@@ -403,7 +403,7 @@ The DDNS sequencing is critical — one domain, one DDNS container, at all times
 handback sequence stops remote DDNS first, rsyncs, starts containers, starts local
 DDNS last. Split-brain DNS is prevented by design.
 
-**→ Full detail: [README-Failover.md](Failover/README-Failover.md)**
+**→ Full detail: [README-Fallback.md](Fallback/README-Fallback.md)**
 
 ---
 
@@ -710,7 +710,7 @@ If you're setting this up from scratch on two servers:
 
 | README | What It Covers |
 |--------|---------------|
-| [README-Failover.md](Failover/README-Failover.md) | DDNS sequencing, tiered failover, handback, split brain prevention, failover_test.sh |
+| [README-Fallback.md](Fallback/README-Fallback.md) | DDNS sequencing, tiered fallback, handback, split brain prevention, fallback_test.sh |
 | [README-Docker_Essentials.md](Docker_Essentials/README-Docker_Essentials.md) | Two-tier container watchdog, memory limits, dependency ordering, skip list, daily/weekly restarts |
 | [README-Unraid_Essentials.md](unRAID_Essentials/README-Unraid_Essentials.md) | Three-tier system watchdog, WebGUI recovery, inotify tuning, PHP-FPM, log hygiene |
 | [README-Orchestrators.md](Orchestrators/README-Orchestrators.md) | What runs when, execution order, daily/weekly windows, adding jobs |