Onboard Eastern Idaho Info Exchange (post-naming)

[rchlfryn]

Onboard the Eastern Idaho Info Exchange as an info-exchange tenant once their group settles on a name and domain.

This is the original ask from #269. That issue has been re-scoped to deliver the platform-wide info-exchange support (using EWYAIX as the first concrete onboarding); this issue tracks the E Idaho-specific work that follows.

Scope

Once their group settles on a name and domain:

1. NAC registers an EIDIX-style slug in the AFP centers API, with platforms matching an info exchange (forecasts: false, weather: false, warnings: false, stations: true, obs: true).
2. Add the new slug to AVALANCHE_CENTERS in src/utilities/tenancy/avalancheCenters.ts with their real domain as customDomain.
3. Run provisionTenant for the new slug.
4. Production DNS cutover at launch (same playbook as any tenant launch).

Dependencies

• Info exchange tenant support (first onboarding: EWYAIX) #269 (platform-wide info-exchange support).
• E Idaho group settles on a name and a domain.
• NAC registers the new slug.

Context

Per @rustynwac in #269: E Idaho will come online "between now and the fall" (~Aug-Oct 2026), grant-funded.