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/components/clients/client-form.tsx

@@ -34,7 +34,6 @@ interface ClientFormProps {
   client?: {
     id: string;
     fullName: string;
-    nationality?: string | null;
     nationalityIso?: string | null;
     preferredContactMethod?: string | null;
     preferredLanguage?: string | null;
@@ -83,7 +82,6 @@ export function ClientForm({ open, onOpenChange, client }: ClientFormProps) {
     if (client && open) {
       reset({
         fullName: client.fullName,
-        nationality: client.nationality ?? undefined,
         nationalityIso: client.nationalityIso ?? undefined,
         preferredContactMethod:
           (client.preferredContactMethod as CreateClientInput['preferredContactMethod']) ??