feat(3d): meal-box merge, stored mutations, undo, mobile undo UI + i18n ×12

- Merge leftovers into existing meal_box when same recipeId + cookedAt date + frozen + available.
- Store mealBoxMutations JSONB on cooking_sessions for deterministic undo.
- Undo decrements portions/remaining, discards box at zero, appends correction ledger rows.
- Mobile: undo button in cooking/[id].tsx after-flow and meal-boxes.tsx within 24h window.
- i18n undo strings across all 12 locales; parity test green.
- 6 new integration tests: merge, no cross-date merge, frozen split, undo restore, undo discard, ledger invariant.
- Update FAS3 audit doc with 3d semantics.

Closes Fas 3d

apps/mobile/src/locales/en/common.json

@@ -385,5 +385,8 @@
   "scan.diff.undoHint": "Each change can be undone from the item detail view.",
   "cooked.portionsSumExceedsPlanned": "Eaten portions and leftovers cannot exceed the total number of portions.",
   "cooked.undoWindowExpired": "This cooking session can no longer be undone. The 24-hour window has expired.",
-  "cooked.leftoverLessThanBox": "Leftovers must be at least as many as the number of meal-box portions."
+  "cooked.leftoverLessThanBox": "Leftovers must be at least as many as the number of meal-box portions.",
+  "mealbox.undoConfirmTitle": "Undo cooking?",
+  "mealbox.undoConfirmBody": "This reverses the inventory deduction and meal box for this cooking session.",
+  "mealbox.undoSuccess": "Cooking session undone."
 }