Feature: Country-Specific Fields (System Collections)

[weilies]

Extend system collection schema to support country-specific field visibility and validation.

What

• Add enabled_for_countries: string[] metadata to field definitions
• Filter fields in API responses based on record.country match
• Enforce required validation only for applicable countries
• Support multi-country fields (e.g., tax ID for US, CA, MX)

Why

Platform scales across regions; some fields (SSN, EPF) are country-specific. Avoid polluting UI with irrelevant fields.