IBAN Country Code Mismatch Fix

Resolve frequent IBAN validation failures caused by country-code and bank-rule inconsistencies.

1. Compare IBAN prefix with expected account jurisdiction rules.

2. Validate IBAN length and structure for the detected country.

3. Recalculate check digits after any formatting normalization.

4. Reject mixed separators and hidden unicode characters.

5. Align onboarding UI hints with backend country validations.

6. Log failures by country to detect integration regressions.