phsl / new-api

- 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