fix(tests): Add missing addFolderToLibrary call to TestMediaItemISBNNormalization

- TestMediaItemISBNNormalization was missing library folder creation
- Caused HTTP 400 errors when creating media items
- addFolderToLibrary call was accidentally removed from line 73
- Tests now properly create library with folder before adding media items

This fixes the root cause of ISBN normalization test failures where
media-item creation failed due to missing library folder requirement.

Dockerfile

@@ -59,7 +59,7 @@ ENV RATE_LIMIT_ENABLED=false
 ENV REQUESTS_PER_MINUTE=1000
 
 # Default command for running tests
-CMD ["go", "test", "./cmd/server/tests", "-v", "-timeout", "5m"]
+CMD ["go", "test", "./cmd/server/tests", "-v", "-timeout", "5m", "-parallel=1"]
 
 # Final stage
 FROM alpine:latest

cmd/server/tests/media_item_isbn_test.go

@@ -69,6 +69,9 @@ func TestMediaItemISBNNormalization(t *testing.T) {
 	token := loginTestUser(t, setup.Server, setup.DB)
 	libID := createTestLibrary(t, setup.Server, token, "test-isbn-lib")
 
+	// Add a folder to the library (required before adding media items)
+	addFolderToLibrary(t, setup.Server, token, libID, "/app/uploads")
+
 	// Test ISBN normalization cases
 	testCases := []struct {
 		name     string
@@ -210,7 +213,7 @@ func TestMediaItemISBNEdgeCases(t *testing.T) {
 
 	token := loginTestUser(t, setup.Server, setup.DB)
 	libID := createTestLibrary(t, setup.Server, token, "test-isbn-edge-lib")
-	addFolderToLibrary(t, setup.Server, token, libID, "/test/folder")
+	addFolderToLibrary(t, setup.Server, token, libID, "/app/uploads")
 
 	t.Run("Empty ISBN should be accepted", func(t *testing.T) {
 		payload := map[string]interface{}{
@@ -295,7 +298,7 @@ func TestMediaItemsPagination(t *testing.T) {
 
 	token := loginTestUser(t, setup.Server, setup.DB)
 	libID := createTestLibrary(t, setup.Server, token, "test-pagination-lib")
-	addFolderToLibrary(t, setup.Server, token, libID, "/test/folder")
+	addFolderToLibrary(t, setup.Server, token, libID, "/app/uploads")
 
 	// Create some test media items
 	for i := 1; i <= 5; i++ {
@@ -427,7 +430,7 @@ func TestMediaItemLibraryRequirement(t *testing.T) {
 
 	t.Run("Create media-item with existing library should succeed", func(t *testing.T) {
 		libID := createTestLibrary(t, setup.Server, token, "test-req-lib")
-		addFolderToLibrary(t, setup.Server, token, libID, "/test/folder")
+		addFolderToLibrary(t, setup.Server, token, libID, "/app/uploads")
 
 		payload := map[string]interface{}{
 			"title":      "Valid Book",
@@ -465,7 +468,7 @@ func TestUpdateMediaItemISBN(t *testing.T) {
 
 	token := loginTestUser(t, setup.Server, setup.DB)
 	libID := createTestLibrary(t, setup.Server, token, "test-update-lib")
-	addFolderToLibrary(t, setup.Server, token, libID, "/test/folder")
+	addFolderToLibrary(t, setup.Server, token, libID, "/app/uploads")
 
 	// First create a media item
 	createPayload := map[string]interface{}{