fix(lint): resolve golangci-lint errors

- Fix errcheck: explicitly ignore tx.Rollback() error in defer
  - When transaction commits successfully, Rollback() returns an error (expected)
  - Use defer func() with explicit error assignment to satisfy linter

- Remove unused connectToService function
  - Function is not currently used (proto files not yet generated)
  - Commented out with TODO for future implementation
  - Prevents unused function lint error

internal/infra/database/client.go

@@ -97,7 +97,9 @@ func createSchemaIfNotExists(ctx context.Context, db *sql.DB, schemaName string)
 	if err != nil {
 		return err
 	}
-	defer tx.Rollback()
+	defer func() {
+		_ = tx.Rollback() // Ignore error - if commit succeeded, rollback will error (expected)
+	}()
 
 	// Check if schema exists
 	var exists bool