fix: auto-create config directory when saving admin config

- save_admin_config_handler now creates parent directory if it doesn't exist
- Prevents 500 error when config/ directory is missing
- Enables first-time config save without manual directory creation

src-tauri/src/proxy.rs

@@ -1154,6 +1154,16 @@ async fn get_admin_config_handler() -> Response {
 
 async fn save_admin_config_handler(axum::extract::Json(payload): axum::extract::Json<serde_json::Value>) -> Response {
     let config_path = get_admin_config_path();
+    
+    // Create parent directory if it doesn't exist
+    if let Some(parent) = config_path.parent() {
+        if !parent.exists() {
+            if let Err(e) = std::fs::create_dir_all(parent) {
+                return (StatusCode::INTERNAL_SERVER_ERROR, format!("Create dir failed: {}", e)).into_response();
+            }
+        }
+    }
+    
     match serde_json::to_string_pretty(&payload) {
         Ok(formatted) => {
             match std::fs::write(&config_path, formatted) {