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>

package.json

@@ -15,6 +15,7 @@
     "@mui/icons-material": "^7.3.5",
     "@mui/material": "^7.3.5",
     "@tailwindcss/typography": "^0.5.10",
+    "@types/iban": "^0.0.35",
     "@types/node": "20.5.7",
     "@zxing/browser": "^0.1.4",
     "@zxing/library": "^0.20.0",
@@ -22,6 +23,7 @@
     "bcrypt": "^5.1.1",
     "clsx": "^2.0.0",
     "daisyui": "^4.5.0",
+    "iban": "^0.0.14",
     "is-ua-webview": "^1.1.2",
     "mongodb": "^6.3.0",
     "next": "^14.0.2",