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-columns.tsx

@@ -14,11 +14,12 @@ import {
 } from '@/components/ui/dropdown-menu';
 import { Badge } from '@/components/ui/badge';
 import { TagBadge } from '@/components/shared/tag-badge';
+import { getCountryName } from '@/lib/i18n/countries';
 
 export interface ClientRow {
   id: string;
   fullName: string;
-  nationality: string | null;
+  nationalityIso: string | null;
   source: string | null;
   archivedAt: string | null;
   createdAt: string;
@@ -78,11 +79,14 @@ export function getClientColumns({
     },
     {
       id: 'nationality',
-      accessorKey: 'nationality',
+      accessorKey: 'nationalityIso',
       header: 'Nationality',
-      cell: ({ getValue }) => (
-        <span className="text-muted-foreground">{(getValue() as string | null) ?? '—'}</span>
-      ),
+      cell: ({ getValue }) => {
+        const iso = getValue() as string | null;
+        return (
+          <span className="text-muted-foreground">{iso ? getCountryName(iso, 'en') : '—'}</span>
+        );
+      },
     },
     {
       id: 'source',