fix(store): scope SetDomainStatus by project (IDOR); scheduler reuses DeriveStatus

handleCheck's error branch wrote last_check_status via an id-only UPDATE, so
an authenticated caller's own valid project id paired with a foreign domain
id in the URL could flip a stranger's domain to "error" even though Check
itself is project-scoped and would 404/error out first. Add project_id to
the WHERE clause (queries/domains.sql + generated db/domains.sql.go), thread
projectID through Store/TenantStore/SchedStore SetDomainStatus, and pass pid
from context at both call sites in handleCheck plus the scheduler.

Also collapse checkDomain's inline status derivation in scheduler.go into a
call to service.DeriveStatus, the same helper handleCheck already uses, so
there's a single source of truth for "drift vs in_sync" instead of two
copies that could drift apart.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BwxdSt4reTm7Dj1oxRvpP3

internal/scheduler/scheduler_test.go

@@ -62,7 +62,11 @@ func (m *mockStore) GetDomainStatus(ctx context.Context, domainID uuid.UUID) (st
 	return StatusUnknown, nil
 }
 
-func (m *mockStore) SetDomainStatus(ctx context.Context, domainID uuid.UUID, status string) error {
+// SetDomainStatus ignores projectID here — this in-memory fake is keyed by
+// domainID alone and isn't exercising the IDOR scoping itself (that's
+// covered at the store layer / API handler level); it exists only to match
+// the SchedStore interface signature.
+func (m *mockStore) SetDomainStatus(ctx context.Context, domainID, projectID uuid.UUID, status string) error {
 	m.mu.Lock()
 	defer m.mu.Unlock()
 	m.status[domainID] = status