feat: view and edit a transaction's note from the list

Transactions can carry a `notes` field (set via the API — e.g. the
currency-conversion metadata on this user's imported historical data), but
there was no way to see it in the UI at all.

TransactionsTable now shows a note icon next to edit/delete, only when a
transaction actually has one, opening a dialog with the text. The edit
form's `notes` field was already wired end to end (state, payload) but had
no input in the JSX — added it, since a view-only note with no way to edit
or clear it would be a dead end.

Also fixed e2e/run.sh's readiness check, found while running the full
suite for this change: it polled `/` (nginx, answers almost immediately)
instead of `/api/health`, so the first test could start before the backend
finished migrating/seeding and fail trying to parse nginx's HTML error
page as JSON.

frontend/src/lib/i18n.ts

@@ -160,6 +160,9 @@ const ru = {
   "transactions.form.categoryLabel": "Категория",
   "transactions.form.noCategory": "Без категории",
   "transactions.form.merchantLabel": "Продавец (необязательно)",
+  "transactions.form.notesLabel": "Заметка (необязательно)",
+  "transactions.viewNote": "Посмотреть заметку",
+  "transactions.noteDialogTitle": "Заметка",
   "transactions.form.errorSelectAccount": "Выберите счёт",
   "transactions.form.errorSelectDestination": "Выберите счёт назначения для перевода",
   "transactions.form.errorSameAccount": "Счёт назначения должен отличаться от исходного счёта",
@@ -486,6 +489,9 @@ const en: Record<keyof typeof ru, string> = {
   "transactions.form.categoryLabel": "Category",
   "transactions.form.noCategory": "No category",
   "transactions.form.merchantLabel": "Merchant (optional)",
+  "transactions.form.notesLabel": "Note (optional)",
+  "transactions.viewNote": "View note",
+  "transactions.noteDialogTitle": "Note",
   "transactions.form.errorSelectAccount": "Select an account",
   "transactions.form.errorSelectDestination": "Select a destination account for the transfer",
   "transactions.form.errorSameAccount": "The destination account must be different from the source account",