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: 1f6cf0eafa. Sections: 12. Findings: 2/7/10/4/6.

internal/service/job.go

@@ -189,8 +189,8 @@ func (s *JobService) GetJobStatus(ctx context.Context, jobID string) (*domain.Jo
 	return job, nil
 }
 
-// CancelJobWithContext cancels a pending or running job.
-func (s *JobService) CancelJobWithContext(ctx context.Context, jobID string) error {
+// CancelJob cancels a pending or running job (handler interface method).
+func (s *JobService) CancelJob(ctx context.Context, jobID string) error {
 	job, err := s.jobRepo.Get(ctx, jobID)
 	if err != nil {
 		return fmt.Errorf("failed to fetch job: %w", err)
@@ -208,13 +208,8 @@ func (s *JobService) CancelJobWithContext(ctx context.Context, jobID string) err
 	return nil
 }
 
-// CancelJob cancels a job (handler interface method).
-func (s *JobService) CancelJob(id string) error {
-	return s.CancelJobWithContext(context.Background(), id)
-}
-
 // ListJobs returns paginated jobs with optional filtering (handler interface method).
-func (s *JobService) ListJobs(status, jobType string, page, perPage int) ([]domain.Job, int64, error) {
+func (s *JobService) ListJobs(ctx context.Context, status, jobType string, page, perPage int) ([]domain.Job, int64, error) {
 	if page < 1 {
 		page = 1
 	}
@@ -222,7 +217,7 @@ func (s *JobService) ListJobs(status, jobType string, page, perPage int) ([]doma
 		perPage = 50
 	}
 
-	allJobs, err := s.jobRepo.List(context.Background())
+	allJobs, err := s.jobRepo.List(ctx)
 	if err != nil {
 		return nil, 0, fmt.Errorf("failed to list jobs: %w", err)
 	}
@@ -263,14 +258,13 @@ func (s *JobService) ListJobs(status, jobType string, page, perPage int) ([]doma
 }
 
 // GetJob returns a single job (handler interface method).
-func (s *JobService) GetJob(id string) (*domain.Job, error) {
-	return s.jobRepo.Get(context.Background(), id)
+func (s *JobService) GetJob(ctx context.Context, id string) (*domain.Job, error) {
+	return s.jobRepo.Get(ctx, id)
 }
 
 // ApproveJob approves a renewal job that is awaiting approval.
 // Transitions the job from AwaitingApproval to Pending so the scheduler picks it up.
-func (s *JobService) ApproveJob(id string) error {
-	ctx := context.Background()
+func (s *JobService) ApproveJob(ctx context.Context, id string) error {
 	job, err := s.jobRepo.Get(ctx, id)
 	if err != nil {
 		return fmt.Errorf("job not found: %w", err)
@@ -290,8 +284,7 @@ func (s *JobService) ApproveJob(id string) error {
 
 // RejectJob rejects a renewal job that is awaiting approval.
 // Transitions the job to Cancelled with a rejection reason.
-func (s *JobService) RejectJob(id string, reason string) error {
-	ctx := context.Background()
+func (s *JobService) RejectJob(ctx context.Context, id string, reason string) error {
 	job, err := s.jobRepo.Get(ctx, id)
 	if err != nil {
 		return fmt.Errorf("job not found: %w", err)