Cache free-mode country access

[jahooma]

Summary

Adds a Postgres-backed free-mode country/privacy cache keyed by user and hashed client IP so scaled web instances can reuse IPinfo decisions.
Wires the chat completions free-mode country gate through the cache with safe fallback logging, preserves raw-IP privacy, and includes TTLs for allowed, VPN/proxy, country-blocked, and transient-failure outcomes.
Adds the Drizzle migration/schema metadata and focused tests for cache hits, misses, refreshes, and TTL behavior.

Validation

• bun test web/src/server/tests/free-mode-country-access-cache.test.ts web/src/server/tests/free-mode-country.test.ts web/src/app/api/v1/chat/completions/tests/completions.test.ts
• bun --cwd web typecheck
• bun --cwd packages/internal typecheck
• bunx prettier --check packages/internal/src/db/migrations/meta/_journal.json packages/internal/src/db/migrations/meta/0051_snapshot.json