add-integrationlisted

# Adding a new third-party integration Jira and Linear are the model: per-workspace credentials, a 90s auth-health poller, a settings page with status banner + reconnect CTA, link/import buttons that gate on availability. New integrations should **reuse the shared shapes** rather than copying either. ## Backend (`apps/backend/internal/<name>/`) - Mirror the package layout: `service.go`, `store.go`, `client.go`, `provider.go`, `handlers.go`, `models.go`, `poller.go`. Expose `Provide(writer, reader *sqlx.DB, secrets SecretStore, eventBus bus.EventBus, log *logger.Logger) (*Service, func() error, error)`. Pass `nil` for `eventBus` when the integration doesn't publish events; both Jira and Linear take and use it for issue-watch publishing. - Use `internal/integrations/secretadapter` instead of writing your own upsert wrapper around `secrets.SecretStore`. The adapter satisfies any per-integration `SecretStore` interface shaped as `{Reveal, Set, Delete, Exists}`. - Use `internal/integrations/healthpoll` for the auth-health loop. Implement the `Prober` interface (`ListConfiguredWorkspaces` + `RecordAuthHealth`) on a small adapter and let `healthpoll.New("name", prober, log)` own Start/Stop/ticker. Keep integration-specific loops (JQL polling, webhook reconciliation, etc.) separate, like jira's issue-watch loop. - Wire the service via a per-domain `init<Name>Service(...)` helper in `cmd/kandev/services.go`, not inline in `provideServices`. - Ship a `mock_client.go` + `mock_control