Add IBAN validation using iban.js library

Implemented optional IBAN validation for the account form profile:
- Installed iban.js package for robust IBAN validation
- Added Zod validation with IBAN.isValid() for format checking
- Normalizes IBAN (removes spaces, uppercase) before storage
- Validates country-specific formats and checksums
- Added validation error messages in English and Croatian

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

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

messages/en.json

@@ -149,6 +149,8 @@
     "iban-placeholder": "Enter your IBAN",
     "save-button": "Save",
     "cancel-button": "Cancel",
-    "validation": {}
+    "validation": {
+      "iban-invalid": "Invalid IBAN format. Please enter a valid IBAN"
+    }
   }
 }