Update mutable business profile fields (PATCH semantics).

Fields not present in the body are left untouched. Identity fields (registration_number, country) and verification-state fields (kyb_status, kyb_level, verification_mode, sumsub_applicant_id) are intentionally not editable here.

Once a business has been verified, the fields used in the verification decision — company_name and tax_id — become locked. Changing them after the fact would silently drift the on-record identity from what the KYB provider / external attestation evaluated. Operational fields (legal_address, contact_email) stay editable so a business that relocates or changes ops contact doesn't need a re-verify. To change a locked field, superadmin must run kyb-reset first.

"Verified" is checked redundantly so the lock survives data inconsistencies (e.g. legacy rows where verification_source is NONE but kyb_status is APPROVED, or rows where Sumsub created an applicant but the webhook hasn't landed yet):

• kyb_status == approved (urbanpayx-decided approval)
• external_verification_status == verified (external attestation)
• verification_source != none (canonical post-decision state)
• sumsub_applicant_id is not None (Sumsub already saw this identity)