feat: add search to Transactions tab, spanning all history

Lets the user find a past purchase by keyword instead of paging through
months manually — search hits description/merchant/notes and ignores the
month filter, with a "jump to month" action on each result to view it in
its normal monthly context.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

frontend/src/lib/i18n.ts

@@ -29,6 +29,7 @@ const ru = {
   "common.loading": "Загрузка…",
   "common.back": "Назад",
   "common.next": "Далее",
+  "common.clear": "Очистить",
   "common.cancel": "Отмена",
   "common.save": "Сохранить",
   "common.saving": "Сохранение…",
@@ -138,6 +139,10 @@ const ru = {
   "transactions.allCategories": "Все категории",
   "transactions.failedToLoad": "Не удалось загрузить транзакции.",
   "transactions.noneFound": "Транзакций не найдено.",
+  "transactions.searchPlaceholder": "Поиск по описанию, продавцу или заметке…",
+  "transactions.searchAcrossAllTime": "Поиск ведётся по всем периодам, а не только за выбранный месяц.",
+  "transactions.searchNoneFound": "Ничего не найдено. Попробуйте другой запрос.",
+  "transactions.jumpToMonth": "Перейти к этому месяцу",
   "transactions.confirmDelete": "Удалить транзакцию «{{description}}»?",
   "transactions.transferSuffix": "→ перевод",
   "transactions.sortDateDesc": "Сначала новые",
@@ -358,6 +363,7 @@ const en: Record<keyof typeof ru, string> = {
   "common.loading": "Loading…",
   "common.back": "Back",
   "common.next": "Next",
+  "common.clear": "Clear",
   "common.cancel": "Cancel",
   "common.save": "Save",
   "common.saving": "Saving…",
@@ -467,6 +473,10 @@ const en: Record<keyof typeof ru, string> = {
   "transactions.allCategories": "All categories",
   "transactions.failedToLoad": "Failed to load transactions.",
   "transactions.noneFound": "No transactions found.",
+  "transactions.searchPlaceholder": "Search by description, merchant, or note…",
+  "transactions.searchAcrossAllTime": "Searching across every period, not just the selected month.",
+  "transactions.searchNoneFound": "Nothing found. Try a different search.",
+  "transactions.jumpToMonth": "Jump to this month",
   "transactions.confirmDelete": "Delete transaction “{{description}}”?",
   "transactions.transferSuffix": "→ transfer",
   "transactions.sortDateDesc": "Newest first",