fix(no_NO): use Luhn check digit for Postgiro (0000) BBANs

[DYNOSuprovo]

What does this change

Updates faker.providers.bank.no_NO.Provider.bban to compute a Luhn (modulus 10) check digit when the 4-digit bank register prefix is 0000 (Postgiro), and adds a deterministic regression test in TestNoNo.

What was wrong

Norwegian 11-digit account numbers (BBANs) normally use a MOD11 check digit over all 10 preceding digits. However, when the 4-digit bank register number is 0000 (the Postgiro code), the remaining 7 digits form a Postgiro account number whose check digit uses Luhn (modulus 10), as validated by stdnum.no.kontonr / stdnum.iban.validate. Because no_NO's bban() always applied MOD11, any generated BBAN starting with 0000 (~1 in 10,000 draws) had an invalid Postgiro check digit ~90% of the time, causing TestNoNo.test_iban_stdnum (iban_validator.validate(faker.iban())) to fail whenever 0000 was drawn.

How this fixes it

When first_10.startswith("0000"), bban() computes the check digit over the 6-digit Postgiro account body (first_10[4:]) using calculate_luhn.

Fixes #2464

Checklist

• I have read the documentation about CONTRIBUTING
• I have read the documentation about Coding style
• I have run make lint

[fcurella]

Thank you!