feat(kotlin): forward migration-naming-pattern to check-migration-order [NOJIRA]

[hauke-d]

Summary

• pull-request-kotlin.yml accepts migration-naming-pattern and passes it to the check-migration-order action's naming-pattern, so callers can override the Flyway filename regex enforced on newly added migrations.
• Its default is the action's regex. An empty value can't be used as the default, because a composite action receives '' instead of falling back to its own default, and the script requires a non-empty pattern.
• Documented in docs/workflow-guide.md and CLAUDE.md.

Why

Repos whose migration filenames don't follow the default V<yyyy>.<mm>.<dd>.<hh>.<mm>__*.sql shape had no way to adjust the check through the shared workflow.

Test plan

• Caller that doesn't set the input: Check Migration Order behaves as before
• Caller that sets migration-naming-pattern: a new migration is validated against the custom pattern