refactor: switch to a dynamic theme based on css variables

[HyperLife1119]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/NG-ZORRO/ng-zorro-antd/blob/master/CONTRIBUTING.md#commit
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

[ ] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[x] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Documentation content changes
[ ] Application (the showcase website) / infrastructure changes
[ ] Other... Please describe:

What is the current behavior?

Issue Number: N/A

What is the new behavior?

[WARNING] Deprecated inline execution of JavaScript has been enabled ("javascriptEnabled") [plugin angular-less]

    components/style/color/bezierEasing.less:110:0:
      110 │ .bezierEasingMixin();
          ╵ ^

  JavaScript found within less stylesheets may be executed at build time. [https://lesscss.org/usage/#less-options]
  Support for "javascriptEnabled" may be removed from the Angular CLI starting with Angular v19.
  The plugin "angular-less" was triggered by this import

要消除 angular-less javascriptEnabled 警告，我们需要将 antd less 文件中的所有 inline-js 用法全部替换为新的 @plugin 用法。

作为第一步，我们需要移除 antd-theme-generator 这个第三方依赖，因为它在内部使用了 inline-js 特性。

ZORRO 使用 antd-theme-generator 生成主题文件（less），用于文档站点的动态主题。在这个 PR 中，我们将文档站点切换到基于 css variables 的动态主题方式。

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

[zorro-bot]

This preview will be available after the AzureCI is passed.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.57%. Comparing base (8c247db) to head (072ed21).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #8545   +/-   ##
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  Coverage   91.57%   91.57%           
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  Files         532      532           
  Lines       18334    18334           
  Branches     2801     2801           
=======================================
+ Hits        16789    16790    +1     
+ Misses       1227     1226    -1     
  Partials      318      318           

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[Laffery]

LGTM