Fix: harden bootstrap worker flow

Backend/internal/worker/runner_test.go

@@ -8,6 +8,7 @@ import (
 	"strings"
 	"sync"
 	"testing"
+	"time"
 
 	"moku-backend/internal/jobs"
 )
@@ -109,13 +110,53 @@ func TestRunnerMarksFailedWhenHandlerMissing(t *testing.T) {
 	}
 }
 
+func TestRunnerRetriesClaimErrors(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	store := &fakeJobStore{
+		claimErrors: []error{errors.New("relation \"background_jobs\" does not exist")},
+		job: &jobs.Job{
+			ID:   "job-4",
+			Kind: jobs.KindBootstrapStructureMaterialize,
+		},
+		cancel: cancel,
+	}
+	runner := NewRunner(store, slog.New(slog.NewTextHandler(io.Discard, nil)), time.Millisecond)
+
+	handlerCalled := false
+	runner.Register(jobs.KindBootstrapStructureMaterialize, func(ctx context.Context, job jobs.Job) error {
+		handlerCalled = true
+		return nil
+	})
+
+	if err := runner.Run(ctx); err != nil {
+		t.Fatalf("runner returned error: %v", err)
+	}
+
+	if !handlerCalled {
+		t.Fatal("expected handler to be called after claim retry")
+	}
+	if store.claimAttempts < 2 {
+		t.Fatalf("expected at least two claim attempts, got %d", store.claimAttempts)
+	}
+	if len(store.succeeded) != 1 || store.succeeded[0] != "job-4" {
+		t.Fatalf("expected job to be marked succeeded once, got %#v", store.succeeded)
+	}
+	if len(store.failed) != 0 {
+		t.Fatalf("expected no failed jobs, got %#v", store.failed)
+	}
+}
+
 type fakeJobStore struct {
-	mu        sync.Mutex
-	job       *jobs.Job
-	claimed   bool
-	succeeded []string
-	failed    []fakeFailure
-	cancel    context.CancelFunc
+	mu            sync.Mutex
+	job           *jobs.Job
+	claimed       bool
+	claimErrors   []error
+	claimAttempts int
+	succeeded     []string
+	failed        []fakeFailure
+	cancel        context.CancelFunc
 }
 
 type fakeFailure struct {
@@ -126,6 +167,13 @@ type fakeFailure struct {
 func (store *fakeJobStore) ClaimNext(ctx context.Context) (*jobs.Job, error) {
 	store.mu.Lock()
 	defer store.mu.Unlock()
+	store.claimAttempts++
+
+	if len(store.claimErrors) > 0 {
+		err := store.claimErrors[0]
+		store.claimErrors = store.claimErrors[1:]
+		return nil, err
+	}
 
 	if store.claimed || store.job == nil {
 		return nil, nil