fix(common): lock registry prevents EXIT trap overwrite orphaning locks

Scripts calling acquire_lock followed by acquire_rsync_lock (rsync.sh)
or a custom EXIT trap (resource_watchdog.sh) would overwrite the lock
release trap, leaving the first lock file behind on exit.

Replace per-acquire trap with a _LOCK_FILES registry. _register_lock()
appends each lock file to the array and sets a single _release_all_locks
trap. All acquired locks release together on exit regardless of how many
traps are subsequently set or overwritten.

resource_watchdog.sh: chain _release_all_locks into both its custom trap
and the state-persisted disarm path so the lock releases in all exit paths.

Watchdogs/resource_watchdog.sh

@@ -151,7 +151,7 @@ _rw_trap_restart_stopped() {
         fi
     done
 }
-trap _rw_trap_restart_stopped EXIT
+trap "_release_all_locks; _rw_trap_restart_stopped" EXIT
 
 # ==============================================================================================
 # ━━━ State Helpers ━━━
@@ -580,6 +580,6 @@ fi
 # ==============================================================================================
 rm_state_set "rm_paused_containers" "$PAUSED_LIST"
 rm_state_set "rm_stopped_containers" "$STOPPED_LIST"
-trap - EXIT  # state persisted — stopped containers recorded, trap no longer needed
+trap "_release_all_locks" EXIT  # state persisted — disable restart trap, keep lock cleanup
 # Touch state file each run so docker_watchdog stale guard sees fresh mtime
 touch "$RW_STATE_FILE" 2>/dev/null