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/client/grpc/auth_client.go

@@ -50,26 +50,27 @@ func (c *AuthClient) Logout(ctx context.Context, refreshToken string) error {
 	return fmt.Errorf("not implemented: proto files not yet generated")
 }
 
-// connectToService discovers and connects to a service instance.
-func connectToService(ctx context.Context, reg registry.ServiceRegistry, serviceName string) (*grpc.ClientConn, error) {
-	instances, err := reg.Discover(ctx, serviceName)
-	if err != nil {
-		return nil, fmt.Errorf("failed to discover service %s: %w", serviceName, err)
-	}
-
-	if len(instances) == 0 {
-		return nil, fmt.Errorf("no instances found for service %s", serviceName)
-	}
-
-	// Use the first healthy instance (load balancing can be added later)
-	instance := instances[0]
-	address := fmt.Sprintf("%s:%d", instance.Address, instance.Port)
-
-	// Create gRPC connection
-	conn, err := grpc.NewClient(address, grpc.WithTransportCredentials(insecure.NewCredentials()))
-	if err != nil {
-		return nil, fmt.Errorf("failed to connect to %s at %s: %w", serviceName, address, err)
-	}
-
-	return conn, nil
-}
+// TODO: connectToService will be implemented when proto files are generated
+// This function will discover and connect to a service instance via gRPC.
+// func connectToService(ctx context.Context, reg registry.ServiceRegistry, serviceName string) (*grpc.ClientConn, error) {
+// 	instances, err := reg.Discover(ctx, serviceName)
+// 	if err != nil {
+// 		return nil, fmt.Errorf("failed to discover service %s: %w", serviceName, err)
+// 	}
+//
+// 	if len(instances) == 0 {
+// 		return nil, fmt.Errorf("no instances found for service %s", serviceName)
+// 	}
+//
+// 	// Use the first healthy instance (load balancing can be added later)
+// 	instance := instances[0]
+// 	address := fmt.Sprintf("%s:%d", instance.Address, instance.Port)
+//
+// 	// Create gRPC connection
+// 	conn, err := grpc.NewClient(address, grpc.WithTransportCredentials(insecure.NewCredentials()))
+// 	if err != nil {
+// 		return nil, fmt.Errorf("failed to connect to %s at %s: %w", serviceName, address, err)
+// 	}
+//
+// 	return conn, nil
+// }

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