Flatten backends package structure

pkg/backends/backend.go

@@ -8,3 +8,15 @@ const (
 	BackendTypeVllm     BackendType = "vllm"
 	// BackendTypeMlxVlm BackendType = "mlx_vlm"  // Future expansion
 )
+
+type Options struct {
+	BackendType    BackendType    `json:"backend_type"`
+	BackendOptions map[string]any `json:"backend_options,omitempty"`
+
+	Nodes map[string]struct{} `json:"-"`
+
+	// Backend-specific options
+	LlamaServerOptions *LlamaServerOptions `json:"-"`
+	MlxServerOptions   *MlxServerOptions   `json:"-"`
+	VllmServerOptions  *VllmServerOptions  `json:"-"`
+}