fix(quick-13): resolve lint issues in main source files

- Fix errcheck for db.Close() in testhelper.go
- Fix errcheck, nlreturn, wsl, gofumpt issues in genevents/main.go
- Fix gofumpt and wsl issues in library.go

backend/favorites/config_test.go

@@ -31,6 +31,7 @@ func TestFavoritesConfig_Validate_InvalidIconStyle(t *testing.T) {
 	t.Parallel()
 
 	c := &Config{IconStyle: "diamond"}
+
 	err := c.Validate()
 	if err == nil {
 		t.Fatal("Validate() expected error for unknown icon style, got nil")