Make PARTNERSHIP_ENABLED the authoritative gate for all cross-server operations

Adds require_partnership() to common.sh — exits cleanly when PARTNERSHIP_ENABLED=false.
Removes FALLBACK_PARTNERSHIP_REQUIRED toggle — partnership is now always required,
not optional. Cross-server scripts (rsync, conf sync, fallback, arr sync, play state,
backup verify) all call require_partnership after detect_hosts.

System_Essentials/conf_cache_restore.sh

@@ -27,6 +27,7 @@ source "$SCRIPT_DIR/../load_config.sh"
 
 parse_args "$@"
 detect_hosts
+require_partnership
 
 RAM_CACHE="/tmp/.cache/vv/d"
 SAVE_DIR="/boot/config/.cache/vv/d"

System_Essentials/conf_cache_save.sh

@@ -23,6 +23,7 @@ source "$SCRIPT_DIR/../load_config.sh"
 
 parse_args "$@"
 detect_hosts
+require_partnership
 
 RAM_CACHE="/tmp/.cache/vv/d"
 SAVE_DIR="/boot/config/.cache/vv/d"

System_Essentials/conf_sync.sh

@@ -48,6 +48,7 @@ for arg in "$@"; do
 done
 parse_args "${FILTERED_ARGS[@]}"
 detect_hosts
+require_partnership
 
 if [[ "${CONF_SYNC_ENABLED:-true}" == false ]]; then
     log "CONF_SYNC_ENABLED=false — skipping"