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/app/api/public/interests/route.ts

@@ -144,7 +144,6 @@ export async function POST(req: NextRequest) {
               name: data.company.name,
               legalName: data.company.legalName ?? null,
               taxId: data.company.taxId ?? null,
-              incorporationCountry: data.company.incorporationCountry ?? null,
               incorporationCountryIso: data.company.incorporationCountryIso ?? null,
               incorporationSubdivisionIso: data.company.incorporationSubdivisionIso ?? null,
               status: 'active',
@@ -216,10 +215,8 @@ export async function POST(req: NextRequest) {
             label: 'Primary',
             streetAddress: data.address.street ?? null,
             city: data.address.city ?? null,
-            stateProvince: data.address.stateProvince ?? null,
             subdivisionIso: data.address.subdivisionIso ?? null,
             postalCode: data.address.postalCode ?? null,
-            country: data.address.country ?? null,
             countryIso: data.address.countryIso ?? null,
             isPrimary: true,
           });