refactor: split backend into standalone server project

Remove embedded frontend and workflow editor assets, add standalone API deployment configuration, and retain the current backend service updates.

internal/bootstrap/server_route_test.go

@@ -183,7 +183,7 @@ func TestNewServerDoesNotExposeLegacyAuthOptions(t *testing.T) {
 	}
 }
 
-func TestNewServerSeparatesAPIStaticAndSPA(t *testing.T) {
+func TestNewServerReturnsJSONNotFoundWithoutFrontendSPA(t *testing.T) {
 	config.SetCurrent(&config.Config{
 		Storage: config.StorageConfig{
 			Local: config.LocalStorageConfig{
@@ -204,7 +204,7 @@ func TestNewServerSeparatesAPIStaticAndSPA(t *testing.T) {
 		contentType string
 	}{
 		{path: "/api/not-exists", wantStatus: http.StatusNotFound, contentType: "application/json"},
-		{path: "/dashboard/not-exists", wantStatus: http.StatusOK, contentType: "text/html"},
+		{path: "/dashboard/not-exists", wantStatus: http.StatusNotFound, contentType: "application/json"},
 	}
 
 	for _, tt := range tests {