Rename tenantFirstName to tenantName with updated validation

- Renamed tenantFirstName to tenantName in BillingLocation interface
- Updated LocationEditForm field to accept full name (first and last)
- Set maximum length to 30 characters for tenant name field
- Updated all database operations to use tenantName
- Changed English label from "Tenant First Name" to "Tenant First and Last Name"
- Updated Croatian translations to match (Ime i prezime podstanara)
- Updated form validation schema and error messages
- Removed old tenantLastName-related translations

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

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

messages/hr.json

@@ -139,10 +139,8 @@
     "tenant-2d-code-legend": "2D BARKOD ZA PODSTANARA",
     "tenant-2d-code-info": "2D barkod omogućuje podstanaru da brzo i jednostavno na vaš IBAN uplati iznos koji vam duguje za plaćene režije. Barkod će biti prikazan kada podstanar otvori poveznicu na obračun za zadani mjesec.",
     "tenant-2d-code-toggle-label": "generiraj 2D barkod",
-    "tenant-first-name-label": "Ime podstanara",
-    "tenant-first-name-placeholder": "Unesite ime podstanara",
-    "tenant-last-name-label": "Prezime podstanara",
-    "tenant-last-name-placeholder": "Unesite prezime podstanara",
+    "tenant-name-label": "Ime i prezime podstanara",
+    "tenant-name-placeholder": "Unesite ime i prezime podstanara",
     "tenant-street-label": "Ulica podstanara",
     "tenant-street-placeholder": "Unesite ulicu podstanara",
     "tenant-town-label": "Grad podstanara",
@@ -174,8 +172,7 @@
     "update-all-months": "sve mjesece",
     "validation": {
       "location-name-required": "Ime nekretnine je obavezno",
-      "tenant-first-name-required": "nedostaje ime podstanara",
-      "tenant-last-name-required": "nedostaje prezime podstanara",
+      "tenant-name-required": "nedostaje ime i prezime podstanara",
       "tenant-street-required": "nedostaje ulica podstanara",
       "tenant-town-required": "nedostaje grad podstanara",
       "tenant-email-required": "nedostaje email podstanara",