fix(home): a shelf move acts on the order shown, one write at a time

- During a budget switch the rail shows the previous budget's payload
  (keepPreviousData) while the new key is empty; the move read that empty
  cache, found no tile and silently did nothing. It now acts on the order
  the rail rendered.
- A refused move was undone only by a re-read; when that read failed too,
  the shelf kept showing the order the user had just been told was not
  saved. Moves are now written one at a time (the move rows wait, with a
  "saving" note), which makes restoring the shown order correct — the
  overlapping-moves problem that ruled a rollback out cannot occur.

frontend/src/i18n/locales/en/home.json

@@ -38,7 +38,8 @@
     "moveLeft": "Left",
     "moveRight": "Right",
     "moveLast": "To the end",
-    "moveFailed": "Could not reorder the shelf."
+    "moveFailed": "Could not reorder the shelf.",
+    "moveSaving": "Saving the new order…"
   },
   "pin": {
     "menu": "Comfort shelf",

frontend/src/i18n/locales/hu/home.json

@@ -38,7 +38,8 @@
     "moveLeft": "Balra",
     "moveRight": "Jobbra",
     "moveLast": "A polc végére",
-    "moveFailed": "Nem sikerült átrendezni a polcot."
+    "moveFailed": "Nem sikerült átrendezni a polcot.",
+    "moveSaving": "Az új sorrend mentése…"
   },
   "pin": {
     "menu": "Komfort polc",