Configurable locale for faker strategy

[cl8dep]

Summary

The faker strategy uses the Bogus library hardcoded to English locale (new Faker("en")). There is no way to generate locale-appropriate fake data such as Spanish names, German addresses, or French phone numbers.

Current Limitation

FakerStrategy.cs line 13:

private static readonly Faker _faker = new("en");

Proposed Approach

Add a global and per-table locale config:

sanitize:
  faker_locale: "es"   # global default, e.g. "es", "de", "fr", "pt_BR"

  - table: "users"
    faker_locale: "de"  # table-level override
    columns:
      - name: "first_name"
        strategy: "faker"
        faker: "first_name"

Bogus supports ~60 locales. The locale string should be validated against supported Bogus locales during validate.

Acceptance Criteria

• faker_locale is configurable at the top-level sanitize block
• Per-table faker_locale overrides the global value
• Default remains "en" when not set
• validate checks the locale string against supported Bogus locales
• Invalid locale produces a clear error message listing available options