chore(i18n): drop legacy free-text country/nationality columns

Test-data only — no production migration needed (per earlier decision).
Schema is now ISO-only; readers convert ISO codes to localized names where
human-readable output is required (EOI documents, invoices, portal).

Migration 0016 drops:
  - clients.nationality
  - companies.incorporation_country
  - client_addresses.{state_province, country}
  - company_addresses.{state_province, country}

Code paths that previously read free-text values now read the ISO column
and pass through `getCountryName()` / `getSubdivisionName()` for rendering.
Document templates ({{client.nationality}}), portal client view, EOI/
reservation-agreement contexts, and invoice billing addresses all updated.

Public yacht-interest endpoint (/api/public/interests) drops the legacy
fields from its insert path and writes ISO codes only. The Zod validators
no longer accept the legacy fields — older website builds posting raw
'incorporationCountry' / 'country' / 'stateProvince' will get 400s.
Server-side phone normalization is unchanged.

Seed data updated to use ISO codes (GB/FR/ES/GR/SE/IT/GH/MC/PA), spread
across continents to keep test fixtures realistic.

Test assertions updated to match the new render shape (e.g.
'United States' not 'US', 'California' not 'CA').

Vitest: 741 -> 741 (unchanged count; assertions updated, no new tests).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/lib/services/invoices.ts

@@ -13,6 +13,8 @@ import { createAuditLog } from '@/lib/audit';
 import { diffEntity } from '@/lib/entity-diff';
 import { withTransaction } from '@/lib/db/utils';
 import { NotFoundError, ConflictError, ValidationError } from '@/lib/errors';
+import { getCountryName } from '@/lib/i18n/countries';
+import { getSubdivisionName } from '@/lib/i18n/subdivisions';
 import { emitToRoom } from '@/lib/socket/server';
 import { logger } from '@/lib/logger';
 import { generatePdf } from '@/lib/pdf/generate';
@@ -99,9 +101,9 @@ async function resolveBillingEntity(
       ? [
           addressRow.streetAddress,
           addressRow.city,
-          addressRow.stateProvince,
+          addressRow.subdivisionIso ? getSubdivisionName(addressRow.subdivisionIso) : null,
           addressRow.postalCode,
-          addressRow.country,
+          addressRow.countryIso ? getCountryName(addressRow.countryIso, 'en') : null,
         ]
           .filter(Boolean)
           .join(', ')
@@ -126,9 +128,9 @@ async function resolveBillingEntity(
     ? [
         addressRow.streetAddress,
         addressRow.city,
-        addressRow.stateProvince,
+        addressRow.subdivisionIso ? getSubdivisionName(addressRow.subdivisionIso) : null,
         addressRow.postalCode,
-        addressRow.country,
+        addressRow.countryIso ? getCountryName(addressRow.countryIso, 'en') : null,
       ]
         .filter(Boolean)
         .join(', ')