fix: use strings.HasPrefix and delegate export to real cleanup method

- Replace manual string prefix check with strings.HasPrefix (idiomatic Go)
- Refactor CleanupCancelledDeploy export to call the real cleanupCancelledDeploy
  method instead of re-implementing the logic, so tests catch regressions
- Add nil-db guard in Deployment.Save and App.Save to prevent panics when
  models are used without a database connection (e.g. in test exports)
- Fix wsl_v5 lint issue (missing blank line before assignment)

internal/models/app.go

@@ -62,6 +62,10 @@ func NewApp(db *database.Database) *App {
 
 // Save inserts or updates the app in the database.
 func (a *App) Save(ctx context.Context) error {
+	if a.db == nil {
+		return fmt.Errorf("no database connection")
+	}
+
 	if a.exists(ctx) {
 		return a.update(ctx)
 	}

internal/models/deployment.go

@@ -57,6 +57,10 @@ func NewDeployment(db *database.Database) *Deployment {
 
 // Save inserts or updates the deployment in the database.
 func (d *Deployment) Save(ctx context.Context) error {
+	if d.db == nil {
+		return fmt.Errorf("no database connection")
+	}
+
 	if d.ID == 0 {
 		return d.insert(ctx)
 	}

internal/service/deploy/deploy.go

@@ -11,6 +11,7 @@ import (
 	"log/slog"
 	"os"
 	"path/filepath"
+	"strings"
 	"sync"
 	"time"
 
@@ -715,7 +716,7 @@ func (svc *Service) cleanupCancelledDeploy(
 	prefix := fmt.Sprintf("%d-", deployment.ID)
 
 	for _, entry := range entries {
-		if entry.IsDir() && len(entry.Name()) > len(prefix) && entry.Name()[:len(prefix)] == prefix {
+		if entry.IsDir() && strings.HasPrefix(entry.Name(), prefix) {
 			dirPath := filepath.Join(buildDir, entry.Name())
 
 			removeErr := os.RemoveAll(dirPath)
@@ -725,6 +726,7 @@ func (svc *Service) cleanupCancelledDeploy(
 			} else {
 				svc.log.Info("cleaned up build dir from cancelled deploy",
 					"app", app.Name, "path", dirPath)
+
 				_ = deployment.AppendLog(ctx, "Cleaned up build directory")
 			}
 		}

internal/service/deploy/export_test.go

@@ -2,13 +2,11 @@ package deploy
 
 import (
 	"context"
-	"fmt"
 	"log/slog"
-	"os"
-	"path/filepath"
 
 	"git.eeqj.de/sneak/upaas/internal/config"
 	"git.eeqj.de/sneak/upaas/internal/docker"
+	"git.eeqj.de/sneak/upaas/internal/models"
 )
 
 // NewTestService creates a Service with minimal dependencies for testing.
@@ -54,23 +52,13 @@ func (svc *Service) CleanupCancelledDeploy(
 	deploymentID int64,
 	imageID string,
 ) {
-	// We can't create real models.App/Deployment in tests easily,
-	// so we test the build dir cleanup portion directly.
-	buildDir := svc.GetBuildDir(appName)
+	app := models.NewApp(nil)
+	app.Name = appName
 
-	entries, err := os.ReadDir(buildDir)
-	if err != nil {
-		return
-	}
+	deployment := models.NewDeployment(nil)
+	deployment.ID = deploymentID
 
-	prefix := fmt.Sprintf("%d-", deploymentID)
-
-	for _, entry := range entries {
-		if entry.IsDir() && len(entry.Name()) > len(prefix) && entry.Name()[:len(prefix)] == prefix {
-			dirPath := filepath.Join(buildDir, entry.Name())
-			_ = os.RemoveAll(dirPath)
-		}
-	}
+	svc.cleanupCancelledDeploy(ctx, app, deployment, imageID)
 }
 
 // GetBuildDirExported exposes GetBuildDir for testing.