feat(search): 引入拼音搜索

* add pinyin search

* style(highlight): keep theme-aware background

- restore theme-aware .highlight with --highlight-bg

- add highlight vars for light/dark

chore: load pinyin lib before script.js

- ensure pinyin-match.js loads before script.js to avoid runtime dependency issues

docs: add third-party notice for pinyin-match

- add placeholder notice; replace with upstream license after verification

---------

Co-authored-by: neo <neo@example.com>
Co-authored-by: Maintainer (PR Edit) <maintainer@local>

assets/style.css

@@ -157,6 +157,7 @@ html {
     color: var(--text-color);
 }
 
+
 body {
     font-family: var(--font-body);
     font-weight: var(--font-weight-body);