feat(blog): enable 'series' taxonomy

Hugo's default taxonomies (categories, tags) are preserved by listing
them explicitly alongside the new series entry:

    taxonomies:
      category: categories
      tag: tags
      series: series

With this, a post can declare 'series: [Hugo折腾笔记]' in front
matter and Hugo will auto-generate /series/<slug>/ landing pages via
PaperMod's existing taxonomy.html — no custom list template needed.

Archetype picks up a commented '# series: []' example so the next
'hugo new posts/...' session shows the field without having to read
this commit message.

Author: lzm

archetypes/default.md

@@ -6,6 +6,7 @@ draft: true
 # description: "" # SEO 摘要，会出现在 RSS 和 meta description
 # tags: []        # 标签，例如: [Python, 异步]
 # categories: []  # 分类，例如: [编程笔记]
+# series: []      # 系列文章（多篇同系列），例如: ["Hugo折腾笔记"]；按发布时间升序显示
 ShowToc: true      # 是否显示右侧目录（默认开启；如不需要可注释掉）
 TocOpen: false     # 目录默认折叠；改成 true 让目录默认展开
 # cover:

hugo.yaml

@@ -10,6 +10,15 @@ defaultContentLanguage: zh-cn
 defaultContentLanguageInSubdir: false
 languageCode: zh-CN
 
+# ---------- Taxonomies ----------
+# Hugo 默认是 categories + tags；显式列出以保留默认并新增 series。
+# `series` 让任意 post 可以 front-matter 写 `series: [名名]` 即可归入
+# 一个系列——PaperMod 的 taxonomy.html 自动渲染 /series/<名名>/ 列表。
+taxonomies:
+  category: categories
+  tag: tags
+  series: series
+
 # ---------- PaperMod 主题参数 ----------
 params:
   env: production