Rename firstName to ownerName with updated validation

- Renamed firstName to ownerName in UserSettings interface
- Updated UserSettingsForm field to accept full name (first and last)
- Set maximum length to 25 characters for owner name field
- Updated all database operations to use ownerName
- Changed English label from "First Name" to "Your First and Last Name"
- Updated Croatian translations to match (Vaše ime i prezime)
- Updated form validation schema and error messages
- Removed old lastName-related translations
- Updated ViewLocationCard to use ownerName for recipient

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

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

messages/en.json

@@ -189,10 +189,8 @@
     "info-box-message": "By activating this option, a 2D barcode will be included in the monthly statement sent to the tenant, allowing them to make a direct payment to your bank account.",
     "tenant-2d-code-legend": "TENANT 2D CODE",
     "tenant-2d-code-toggle-label": "include 2D code in monthly statements",
-    "first-name-label": "First Name",
-    "first-name-placeholder": "enter your first name",
-    "last-name-label": "Last Name",
-    "last-name-placeholder": "enter your last name",
+    "owner-name-label": "Your First and Last Name",
+    "owner-name-placeholder": "enter your first and last name",
     "street-label": "Street",
     "street-placeholder": "enter your street",
     "town-label": "Town",
@@ -203,8 +201,7 @@
     "save-button": "Save",
     "cancel-button": "Cancel",
     "validation": {
-      "first-name-required": "First name is mandatory",
-      "last-name-required": "Last name is mandatory",
+      "owner-name-required": "Name is mandatory",
       "street-required": "Street is mandatory",
       "town-required": "Town is mandatory",
       "iban-required": "Valid IBAN is mandatory",