Add town and currency fields to user settings

Adds two new fields to user settings form:
- Town field: Text input for city/town (required when 2D code enabled)
- Currency field: Select dropdown with ISO 4217 currency codes (EUR default)

Updates:
- Database schema: Added town and currency fields to UserSettings
- Validation: Both fields required when 2D code is enabled
- Form UI: Added input fields with proper validation and error handling
- Translations: Added Croatian and English labels and error messages
- Currency options: 36 ISO 4217 codes with EUR at top as default

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

app/lib/db-types.ts

@@ -24,8 +24,12 @@ export interface UserSettings {
     lastName?: string | null;
     /** street */
     street?: string | null;
+    /** town */
+    town?: string | null;
     /** IBAN */
     iban?: string | null;
+    /** currency (ISO 4217) */
+    currency?: string | null;
     /** whether to show 2D code in monthly statement */
     show2dCodeInMonthlyStatement?: boolean | null;
 };