Wire UserQuota.MaxChecksPerDay field into the scheduler via the
UserGater: an in-memory daily counter per user
(reset at UTC midnight): gates scheduled executions, with a two-tier
heuristic that skips short-interval jobs first once the budget is 80%
consumed so rare/important checks are not starved by frequent
pings. Planned executions returned by ListPlannedExecutions are marked
with a new ExecutionRateLimited status when the user is over
budget. Manual API triggers bypass the quota.
Wire up the checker system to the HTTP layer:
- API controllers for checker operations, options, plans, and results
- Scoped routes at domain and service level
- Admin controllers for checker config and scheduler management
- App initialization: create usecases, start/stop scheduler
- Zone controller updated to include per-service check status
