Regional event registration should support local-region priority or eligibility rules

Issue description:

A player requested that Regional event registration should favor players from the relevant region, either by locking registration to that region or by applying a priority system for eligible local players.

Source:

• Featurebase: https://cardeio.featurebase.app/p/regionals
• Submitted by Sascha N on 2026-04-21

Reported problem:

• The player wanted to attend an EU regional and was unable to secure a spot.
• They report this felt especially frustrating because they had already earned a bye from a Skirmish.
• The underlying ask is not just "add a feature" — it is a fairness/policy problem around how scarce regional seats are allocated.

Customer quote:

• "Pls lock Regionals to Region or do some Prio System for ppl that are in that specific Region. i Wanted to attend at any Regio in EU and didnt get any chance even when i got a bye from a skrimish. Thats very frustrating."

Why this needs triage / product decision:

• This is a policy question as much as a product one.
• We need to decide whether the right answer is hard region-locking, a priority window, a waitlist/lottery approach, or no gating at all.
• We also need clarity on how earned byes should interact with registration priority, if at all.

Suggested success criteria for discovery:

• Product decides whether regional events should enforce region-based eligibility or registration priority.
• If yes, define which user/location/event signals determine eligibility.
• Clarify whether earned byes or other competitive achievements should affect registration priority.
• Define the simplest enforceable workflow that reduces player frustration around regional access.