ClientFlow v4926.7 — fiscal identity guardrails + duplicate NIF handling

Fixes

Rejects invalid company mentions extracted from email identity, including bare TLD/domain fragments such as pt, com, www, and full domains like sementenergias.pt.
Prevents short fragments such as pt from matching inside company names like PLANETOPTION, LDA.
Reduces false fiscal conflicts caused by invalid email identity mentions.
Adds friendly duplicate-NIF handling when editing customers. Editing a customer with a NIF that already belongs to another customer now returns a business conflict instead of a raw PostgreSQL unique violation.

scripts/cleanup_invalid_email_identity_suggestions.py rejects pending/accepted email-identity suggestions created from invalid lookup values such as pt.
scripts/inspect_customer_tax_id_conflict.py lists customers and linked counts for a duplicate NIF conflict.

For the SEMENTENERGIAS case, refresh email identity extraction after installing and reject old invalid suggestions created from pt.