rename: fix remaining failover refs in fallback.sh, fallback_test.sh, array_started.sh, user_script_plug-in.sh

Fallback/fallback_test.sh

@@ -148,7 +148,7 @@ if [[ "$EUID" -ne 0 ]]; then
     exit 1
 fi
 
-# FALLBACK_ENABLED gate — no point testing if failover is disabled
+# FALLBACK_ENABLED gate — no point testing if fallback is disabled
 if [[ "${FALLBACK_ENABLED:-false}" == false ]]; then
     warn "FALLBACK_ENABLED=false — fallback test aborted"
     warn "Enable fallback in master.conf before running this test"
@@ -226,7 +226,7 @@ TOTAL_START=$(date +%s)
 phase_pass() { PHASES_PASS+=("$1"); warn "$ICON_DONE  Phase: $1 — PASSED ✅"; }
 phase_fail() { PHASES_FAIL+=("$1"); error "Phase: $1 — FAILED ❌"; }
 
-# Get Tier 1 containers for this server's failover responsibility
+# Get Tier 1 containers for this server's fallback responsibility
 TIER1_VAR="FALLBACK_${MY_ID}_COVERS_${REMOTE_ID}_TIER1"
 eval "TIER1_CONTAINERS=(\"\${${TIER1_VAR}[@]:-}\")"