Refactor BASE_SPEED definition for clarity

Updated the definition of the `BASE_SPEED` constant to use the nullish coalescing operator (`??`) instead of a ternary operator. This change simplifies the code by ensuring `BASE_SPEED` is set to `viewer.zoomSpeed` if defined, or defaults to `0.015` if not. Retained the existing comment for context.

Author: h2ls

src/BootstrapBlazor/wwwroot/modules/viewer.js

@@ -147,7 +147,7 @@ export default {
 
 
         // 配置缩放速度因子（值越大缩放越快）
-        const BASE_SPEED = viewer.zoomSpeed ? viewer.zoomSpeed : 0.015; // 基础速度
+        const BASE_SPEED = viewer.zoomSpeed ?? 0.015; // 基础速度
 
         const handlerWheel = e => {
             e.preventDefault();