feat(api): Snapshot complete CRUD + enhanced SnapshotInfo

Problem

GET /snapshots lists snapshots but there is no way to retrieve a single snapshot by ID or delete one. The SnapshotInfo schema only exposes snapshotID and names — users cannot see resource specs (vCPU, RAM, disk) or creation time without listing all snapshots and filtering client-side.

Proposed changes

New endpoints

• GET /snapshots/{snapshotID} — return SnapshotInfo for a single snapshot (404 if not found or not owned by team)
• DELETE /snapshots/{snapshotID} — soft-delete a snapshot template, release its aliases, return 204

Enhanced SnapshotInfo

Add four fields populated from the existing ListTeamSnapshotTemplatesRow query result (no new DB queries needed):

Implementation notes

• GET handler resolves the alias via templateCache.ResolveAlias (same path as POST /snapshots/{id}/fork) then calls ListTeamSnapshotTemplates with PageLimit=1.
• DELETE handler reuses the existing unexported softDeleteTemplate helper from template_delete.go and invalidates the template cache.
• api.gen.go is manually maintained (not regenerated from spec); updated by hand following existing patterns.

Start with the existing POST /snapshots/{id}/fork path and its templateCache.ResolveAlias usage, then inspect template_delete.go for softDeleteTemplate. Update api.gen.go by following its existing patterns and use ListTeamSnapshotTemplates with PageLimit=1. Done means single-snapshot GET and soft-delete DELETE behavior match the stated ownership, 404, 204, alias-release, cache-invalidation, and SnapshotInfo field requirements.