This change introduces a validation script to ensure that DNS zone files have their SOA serial
incremented whenever a real DNS record modification is made.

It also validates the format of the SOA serial before checking whether it has been bumped.

The goal is to enforce correct DNS behavior by requiring a serial update only when meaningful
changes occur (e.g. IP change), while ignoring non-significant changes such as extra
spaces that will be corrected during code review.

The validation is integrated as a pre-commit hook and only applies to .zone files.

Ref T2149

Test 1:

• Modify a .zone file (e.g. change an IP)
• Do not update the SOA serial
• Commit

→ The commit should fail with an error

Test 2:

• Make a non-significant change (e.g. extra spaces)
• Do not update the SOA serial
• Commit

→ No error should occur