Adds region-level gating so MICROVM regions are only visible and usable
by orgs with the `hasComputeAccess` feature flag. Admins and explicit
allowlist behavior unchanged.
- New shared helper (`regionAccess.server.ts`) with
`resolveComputeAccess`, `defaultVisibilityFilter`, and
`isComputeRegionAccessible`
- `RegionsPresenter` filters out MICROVM regions for non-compute orgs
- `SetDefaultRegionService` blocks setting a MICROVM region as default
without compute access
- `WorkerGroupService` blocks triggering runs in MICROVM regions without
compute access
- `computeTemplateCreation` refactored to use shared
`resolveComputeAccess`
- Updated snapshot callback schema
nicktrn
e59614a31c