fix(m2-pr-d): thread ctx through Job/Notification/Audit services

Collapse CancelJobWithContext into CancelJob; eliminate 10 context.Background()
hits across the Job+Notification+Audit service cluster by threading ctx
through their handler-facing service interfaces.

Services (ctx-first):
- service/job.go: ListJobs, GetJob, CancelJob, ApproveJob, RejectJob now
  accept ctx; the CancelJobWithContext wrapper is removed (handler callers
  continue to invoke CancelJob, now ctx-aware).
- service/notification.go: ListNotifications, GetNotification, MarkAsRead
  accept ctx.
- service/audit.go: ListAuditEvents, GetAuditEvent accept ctx.

Handlers (interface + callsites):
- handler/jobs.go, handler/notifications.go, handler/audit.go: local
  service interfaces updated, r.Context() threaded at every callsite.

Tests:
- Mock services updated to match the new interfaces (ctx accepted and
  ignored via '_ context.Context' first parameter; Fn closure fields
  unchanged).
- job_test.go / notification_test.go callsites thread context.Background()
  to match production shape.

Verification:
  go build ./...                 ok
  go vet ./...                   ok
  go test -short ./...           ok
  go test -race -short ./...     ok
  golangci-lint run ./...        0 issues

Locked decisions from the M-2 plan:
  D-1 ctx-only signatures (no dual forms)
  D-4 preserve handler method names facing the router
  D-5 domain types stay ctx-free

Audit complete. Commit: 855124a9d9. Sections: 12. Findings: 2/7/10/4/6.

internal/service/audit.go

@@ -110,7 +110,7 @@ func (s *AuditService) ListByAction(ctx context.Context, action string, from, to
 }
 
 // ListAuditEvents returns paginated audit events (handler interface method).
-func (s *AuditService) ListAuditEvents(page, perPage int) ([]domain.AuditEvent, int64, error) {
+func (s *AuditService) ListAuditEvents(ctx context.Context, page, perPage int) ([]domain.AuditEvent, int64, error) {
 	if page < 1 {
 		page = 1
 	}
@@ -123,7 +123,7 @@ func (s *AuditService) ListAuditEvents(page, perPage int) ([]domain.AuditEvent,
 		PerPage: perPage,
 	}
 
-	events, err := s.auditRepo.List(context.Background(), filter)
+	events, err := s.auditRepo.List(ctx, filter)
 	if err != nil {
 		return nil, 0, fmt.Errorf("failed to list audit events: %w", err)
 	}
@@ -143,13 +143,13 @@ func (s *AuditService) ListAuditEvents(page, perPage int) ([]domain.AuditEvent,
 }
 
 // GetAuditEvent returns a single audit event (handler interface method).
-func (s *AuditService) GetAuditEvent(id string) (*domain.AuditEvent, error) {
+func (s *AuditService) GetAuditEvent(ctx context.Context, id string) (*domain.AuditEvent, error) {
 	filter := &repository.AuditFilter{
 		ResourceID: id,
 		PerPage:    1,
 	}
 
-	events, err := s.auditRepo.List(context.Background(), filter)
+	events, err := s.auditRepo.List(ctx, filter)
 	if err != nil {
 		return nil, fmt.Errorf("failed to get audit event: %w", err)
 	}