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/migrations/0016_magical_spyke.sql

@@ -0,0 +1,6 @@
+ALTER TABLE "client_addresses" DROP COLUMN "state_province";--> statement-breakpoint
+ALTER TABLE "client_addresses" DROP COLUMN "country";--> statement-breakpoint
+ALTER TABLE "clients" DROP COLUMN "nationality";--> statement-breakpoint
+ALTER TABLE "companies" DROP COLUMN "incorporation_country";--> statement-breakpoint
+ALTER TABLE "company_addresses" DROP COLUMN "state_province";--> statement-breakpoint
+ALTER TABLE "company_addresses" DROP COLUMN "country";

src/lib/db/migrations/meta/_journal.json

@@ -113,6 +113,13 @@
       "when": 1777391373291,
       "tag": "0015_i18n_columns",
       "breakpoints": true
+    },
+    {
+      "idx": 16,
+      "version": "7",
+      "when": 1777395538988,
+      "tag": "0016_magical_spyke",
+      "breakpoints": true
     }
   ]
 }