i18n(expenses): add missing lowercase 'cheltuială'/'cheltuieli' model labels

Model labels used lowercase (Expense::getModelLabel returns __('cheltuială'))
but dict only had capitalised keys. Filament rendered 'Создать
Cheltuială' as fallback. Now RU shows 'Создать расход' / EN 'Create
expense'.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

lang/en.json

@@ -2034,8 +2034,8 @@
   "capacitate": "capacity",
   "cerere": "lead",
   "cereri": "leads",
-  "cheltuială": "cheltuială",
-  "cheltuieli": "cheltuieli",
+  "cheltuială": "expense",
+  "cheltuieli": "expenses",
   "client": "client",
   "client magazin": "shop customer",
   "clienți": "clients",

lang/ru.json

@@ -2034,8 +2034,8 @@
   "capacitate": "загрузка",
   "cerere": "заявка",
   "cereri": "заявки",
-  "cheltuială": "cheltuială",
-  "cheltuieli": "cheltuieli",
+  "cheltuială": "расход",
+  "cheltuieli": "расходы",
   "client": "клиент",
   "client magazin": "клиент магазина",
   "clienți": "клиенты",