feat(e-billing): customer attribution via buyer identifier - #1026

Summary

• Attribute e-billing documents to Customer by buyer identifier (EN 16931 BT-46 / customer_number), persist that field on invoices, and derive reporting-only company_id from the customer's company assignment.
• Corroborate attributed customers against buyer master data (name, VAT, country, address); mismatches only flag needs_review and never clear attribution.
• Add manual attribution and explicit rematch from Filament (attribution_source auto|manual), with unified company name matching in CompanyNameMatcher).

Packages

• moox/e-billing — matcher, corroborator, Filament actions, config, docs
• moox/invoice — customer_number column / model / builder / draft / factory

Test plan

• Ingest a domestic PDF whose buyer identifier matches exactly one active customer → customer_id set, attribution_source=auto, clean validation path still reachable
• Soft-deleted / inactive customer match → attributed but customer_number = needs_review
• No match / missing identifier → customer_id null; name fallback may set company_id only
• Corroboration divergence (name/VAT/country/address) → needs_review only; customer_id unchanged
• Manual set-attribution from invoice detail → attribution_source=manual; auto rematch does not overwrite manual
• Rematch from detail/list → resets review status, re-runs field validation; confirmed/validated docs refuse automatic overwrite as documented
• Changing attribution after HumanConfirmed/Validated clears attestation back to DbValidated
• Republish e-billing + invoice config/migrations and run package tests

Closes mooxphp/e-billing#23
Closes mooxphp/e-billing#24
Closes mooxphp/e-billing#25
Closes mooxphp/e-billing#27