Merge feat/sqlite-migration: add database schema migration system

This merge brings the SQLite migration system from feat/sqlite-migration branch:

## New Features
- Schema version control with SCHEMA_VERSION constant
- Automatic migration of missing columns for providers table
- Dry-run validation mode for schema compatibility checks
- JSON→SQLite migration feature gate (CC_SWITCH_ENABLE_JSON_DB_MIGRATION)
- Settings reload mechanism after imports

## Test Updates
- Updated tests to use SQLite database instead of config.json
- Removed obsolete import_config_from_path tests (replaced by db.import_sql)
- Fixed MCP tests to use unified McpServer structure (v3.7.0+)
- Updated provider switch tests to reflect no-backfill behavior
- Adjusted error type matching for new error variants

src-tauri/src/commands/import_export.rs

@@ -48,6 +48,11 @@ pub async fn import_config_from_file(
             log::warn!("导入后同步 live 配置失败: {err}");
         }
 
+        // 重新加载设置到内存缓存，确保导入的设置生效
+        if let Err(err) = crate::settings::reload_settings() {
+            log::warn!("导入后重载设置失败: {err}");
+        }
+
         Ok::<_, AppError>(json!({
             "success": true,
             "message": "SQL imported successfully",

src-tauri/src/commands/settings.rs

@@ -18,7 +18,12 @@ pub async fn save_settings(settings: crate::settings::AppSettings) -> Result<boo
 /// 重启应用程序（当 app_config_dir 变更后使用）
 #[tauri::command]
 pub async fn restart_app(app: AppHandle) -> Result<bool, String> {
-    app.restart();
+    // 在后台延迟重启，让函数有时间返回响应
+    tauri::async_runtime::spawn(async move {
+        tokio::time::sleep(tokio::time::Duration::from_millis(100)).await;
+        app.restart();
+    });
+    Ok(true)
 }
 
 /// 获取 app_config_dir 覆盖配置 (从 Store)