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/db/schema/clients.ts

@@ -21,9 +21,7 @@ export const clients = pgTable(
       .notNull()
       .references(() => ports.id),
     fullName: text('full_name').notNull(),
-    nationality: text('nationality'),
-    /** ISO-3166-1 alpha-2 nationality code. Supersedes `nationality`
-     *  after the i18n backfill (PR10) drops the legacy column. */
+    /** ISO-3166-1 alpha-2 nationality code. */
     nationalityIso: text('nationality_iso'),
     preferredContactMethod: text('preferred_contact_method'), // email, phone, whatsapp
     preferredLanguage: text('preferred_language'),
@@ -162,12 +160,10 @@ export const clientAddresses = pgTable(
     label: text('label').notNull().default('Primary'),
     streetAddress: text('street_address'),
     city: text('city'),
-    stateProvince: text('state_province'),
     /** ISO 3166-2 subdivision code (e.g. 'PL-MZ', 'US-CA'). Optional. */
     subdivisionIso: text('subdivision_iso'),
     postalCode: text('postal_code'),
-    country: text('country'),
-    /** ISO-3166-1 alpha-2 country code. Supersedes `country` after backfill. */
+    /** ISO-3166-1 alpha-2 country code. */
     countryIso: text('country_iso'),
     isPrimary: boolean('is_primary').notNull().default(true),
     createdAt: timestamp('created_at', { withTimezone: true }).notNull().defaultNow(),