feat: deutsche Betragsanzeige (eur-Filter) und deutsche GUI-Labels

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

finance/app/templates/transactions.html

@@ -53,7 +53,7 @@
       <td class="account">{{ account_names.get(tx.account_id, tx.account_id) }}</td>
       <td>{{ tx.purpose }}</td>
       <td>{{ tx.counterparty }}</td>
-      <td class="amount {{ 'neg' if tx.amount < 0 else '' }}">{{ '%.2f'|format(tx.amount) }}</td>
+      <td class="amount {{ 'neg' if tx.amount < 0 else '' }}">{{ tx.amount|eur }}</td>
       <td>
         <select name="category_id" data-type="int" hx-ext="json-form"
                 hx-patch="/api/transactions/{{ tx.id }}" hx-trigger="change" hx-swap="none">