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>

tests/integration/document-templates-generate-and-sign.test.ts

@@ -108,7 +108,7 @@ beforeAll(async () => {
   const port = await makePort();
   const client = await makeClient({
     portId: port.id,
-    overrides: { fullName: 'Dual Path Client', nationality: 'US' },
+    overrides: { fullName: 'Dual Path Client', nationalityIso: 'US' },
   });
   await db.insert(clientContacts).values({
     clientId: client.id,
@@ -121,7 +121,7 @@ beforeAll(async () => {
     portId: port.id,
     streetAddress: '1 Wharf Rd',
     city: 'Harbor',
-    country: 'US',
+    countryIso: 'US',
     isPrimary: true,
   });