feat(one-time-downloads): add expiry and retry configuration

Introduce new environment variables to control the behavior of one-time download boxes:
- `WARPBOX_ONE_TIME_DOWNLOAD_EXPIRY_SECONDS`: Sets the lifetime of a one-time box after uploads are complete.
- `WARPBOX_ONE_TIME_DOWNLOAD_RETRY_ON_FAILURE`: Determines whether a box remains available if the ZIP creation or transfer fails.

To support these settings, the ZIP delivery process was refactored to use a temporary file. This ensures that a one-time box is only marked as consumed after the file has been successfully transferred to the client, preventing data loss on network interruptions.

Additionally, added a `DecorateFiles` helper in the box store to reduce code duplication.

lib/boxstore/store_test.go

@@ -47,7 +47,11 @@ func TestStartRetentionBeginsWhenEveryFileIsTerminal(t *testing.T) {
 	}
 }
 
-func TestStartRetentionSkipsOneTimeDownload(t *testing.T) {
+func TestStartRetentionUsesConfiguredOneTimeDownloadExpiry(t *testing.T) {
+	restoreExpiry := OneTimeDownloadExpiry()
+	defer SetOneTimeDownloadExpiry(restoreExpiry)
+	SetOneTimeDownloadExpiry(30)
+
 	manifest := models.BoxManifest{
 		RetentionSecs:   10,
 		OneTimeDownload: true,
@@ -56,11 +60,38 @@ func TestStartRetentionSkipsOneTimeDownload(t *testing.T) {
 			{ID: "two", Status: models.FileStatusReady},
 		},
 	}
+	before := time.Now().UTC()
+
+	startRetentionIfTerminalUnlocked(&manifest)
+
+	if manifest.ExpiresAt.IsZero() {
+		t.Fatal("expected one-time download expiry to start from configured expiry")
+	}
+	if manifest.ExpiresAt.Before(before.Add(29 * time.Second)) {
+		t.Fatalf("expected configured one-time expiry, got %s", manifest.ExpiresAt)
+	}
+	if manifest.ExpiresAt.After(before.Add(31 * time.Second)) {
+		t.Fatalf("expected configured one-time expiry near 30s, got %s", manifest.ExpiresAt)
+	}
+}
+
+func TestStartRetentionSkipsOneTimeDownloadWhenExpiryZero(t *testing.T) {
+	restoreExpiry := OneTimeDownloadExpiry()
+	defer SetOneTimeDownloadExpiry(restoreExpiry)
+	SetOneTimeDownloadExpiry(0)
+
+	manifest := models.BoxManifest{
+		RetentionSecs:   10,
+		OneTimeDownload: true,
+		Files: []models.BoxFile{
+			{ID: "one", Status: models.FileStatusReady},
+		},
+	}
 
 	startRetentionIfTerminalUnlocked(&manifest)
 
 	if !manifest.ExpiresAt.IsZero() {
-		t.Fatalf("expected one-time download box to avoid retention expiry, got %s", manifest.ExpiresAt)
+		t.Fatalf("expected zero one-time expiry to keep expiry unset, got %s", manifest.ExpiresAt)
 	}
 }
 
@@ -115,6 +146,32 @@ func TestListFilesSkipsSymlinks(t *testing.T) {
 	}
 }
 
+func TestThumbnailTasksSkipOneTimeDownloadBoxes(t *testing.T) {
+	restoreUploadRoot := UploadRoot()
+	defer SetUploadRoot(restoreUploadRoot)
+	SetUploadRoot(t.TempDir())
+
+	boxID := "0123456789abcdef0123456789abcdef"
+	if err := os.MkdirAll(BoxPath(boxID), 0755); err != nil {
+		t.Fatalf("MkdirAll returned error: %v", err)
+	}
+	if err := WriteManifest(boxID, models.BoxManifest{
+		OneTimeDownload: true,
+		Files: []models.BoxFile{{
+			ID:       "0123456789abcdef",
+			Name:     "image.png",
+			MimeType: "image/png",
+			Status:   models.FileStatusReady,
+		}},
+	}); err != nil {
+		t.Fatalf("WriteManifest returned error: %v", err)
+	}
+
+	if tasks := collectBoxThumbnailTasks(boxID, 10); len(tasks) != 0 {
+		t.Fatalf("expected no thumbnail tasks for one-time box, got %#v", tasks)
+	}
+}
+
 func TestBoxPasswordUsesBcryptAndVerifiesLegacy(t *testing.T) {
 	restoreUploadRoot := UploadRoot()
 	defer SetUploadRoot(restoreUploadRoot)