🎨 fix: sidebar skeleton background and icon spacing consistency

- Set sidebar skeleton background to use theme variable (--semi-color-bg-0) instead of hardcoded white for better dark mode compatibility
- Apply consistent background to both collapsed and expanded skeleton states
- Ensure sidebar container uses theme background when skeleton is loading
- Remove duplicate margin-right classes from skeleton wrapper components that conflicted with CSS definitions
- Simplify navigation text structure by removing unnecessary div wrappers to improve text truncation
- Add proper text layout styles for better truncation handling when menu items have long names
- Standardize icon-to-text spacing across all sidebar navigation items

web/src/index.css

@@ -71,6 +71,11 @@ code {
   margin-right: 0;
 }
 
+.sidebar-nav .semi-navigation-item-text {
+  flex: 1;
+  min-width: 0;
+}
+
 .semi-navigation-item,
 .semi-navigation-sub-title {
   height: 100% !important;