Feature request: add geographic eligibility / country fields to program schema

[Londonbase]

Hi guys— first off, thanks for building this. I've been using the MCP connector to research affiliate program trends and the data is genuinely useful.

One field I kept reaching for and couldn't find: geographic eligibility. Specifically:

• Which countries can affiliates sign up from?
• Which countries are excluded (if any)?
• Are there any countries where promotion is restricted (e.g. regulated markets)?

Right now I can infer some of this indirectly:

• payout.currency hints at the company's billing base (USD vs EUR)
• payout.methods (PayPal, bank) suggests global accessibility by default
• restrictions sometimes mentions geo limits, but it's freeform and inconsistent

This matters because:

1. For affiliates picking programs to promote, geo eligibility is often the first filter. A creator in India or Brazil currently has no way to filter out programs they can't actually join.

2. For AI agents (which the registry is built for), structured geo data would let agents recommend programs that are actually accessible to a given user.

3. For trend analysis, you could surface insights like "X% of SaaS affiliate programs are globally available" — which would itself be a useful talking point for the registry.

Proposed schema additions:

eligibility:
  countries_allowed: ["global"] # or ["US", "CA", "GB", ...]
  countries_excluded: ["CU", "IR", "KP", "SY"] # sanctions-driven, common
  promotion_restrictions: [] # e.g. "no promotion to EU residents under GDPR-restricted terms"
  tax_forms_required: ["W-8BEN", "W-9"]

I'd suggest countries_allowed: ["global"] as the sensible default for most entries, since the dominant networks (PartnerStack, Rewardful, Impact) pay internationally by default. That keeps the migration cheap — most programs only need an exception list.

Happy to contribute a PR if there's interest. Wanted to file the issue first to check whether this fits the project's direction.

Thanks again — great project.