style: normalize English translation capitalization

- Change uppercase section headers to title case for consistency
- "AUTOMATIC UTILITY BILL FORWARDING" → "Automatic utility bill forwarding"
- "AUTOMATIC RENT NOTIFICATION" → "Automatic rent notification"

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

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

messages/en.json

@@ -154,13 +154,13 @@
     "iban-payment--tenant-town-label": "Tenant Postal Code and Town",
     "iban-payment--tenant-town-placeholder": "enter tenant's town",
 
-    "auto-utility-bill-forwarding-legend": "AUTOMATIC UTILITY BILL FORWARDING",
+    "auto-utility-bill-forwarding-legend": "Automatic utility bill forwarding",
     "auto-utility-bill-forwarding-info": "This option enables automatic forwarding of utility bills to the tenant via email according to the selected forwarding strategy.",
     "auto-utility-bill-forwarding-toggle-label": "forward utility bills",
     "utility-bill-forwarding-strategy-label": "Forward utility bills when ...",
     "utility-bill-forwarding-when-payed": "all items are marked as paid",
     "utility-bill-forwarding-when-attached": "a bill (PDF) is attached to all items",
-    "auto-rent-notification-legend": "AUTOMATIC RENT NOTIFICATION",
+    "auto-rent-notification-legend": "Automatic rent notification",
     "auto-rent-notification-info": "This option enables automatic sending of monthly rent bill to the tenant via email on the specified day of the month.",
     "auto-rent-notification-toggle-label": "send rent notification",
     "rent-due-day-label": "Day of month when rent is due",