chore: 升级 VuePress/Plume 并迁移至 collections 配置

- 将 vuepress 升至 2.0.0-rc.26、vuepress-theme-plume 升至 1.0.0-rc.192

- 用 defineCollections 替代已废弃的 blog + notes，新增 collections.ts 并删除 notes.ts

- 通过 package overrides 将 @vuepress/helper 固定为 rc.123，避免 dev 下 encodeSVG 缺失导致首页白屏

- 新增 .npmrc（legacy-peer-deps）以兼容当前 peer 依赖解析

未包含 docs/.vuepress/dist 等构建产物。

Made-with: Cursor

docs/.vuepress/plume.config.ts

@@ -1,6 +1,6 @@
 import { defineThemeConfig } from 'vuepress-theme-plume'
+import collections from './collections'
 import navbar from './navbar'
-import notes from './notes'
 
 export default defineThemeConfig({
   logo: '/plume.svg',
@@ -21,5 +21,5 @@ export default defineThemeConfig({
   },
 
   navbar,
-  notes,
+  collections,
 })