fix: 安装 Docsy 主题 npm 依赖（Bootstrap/FontAwesome）

Docsy 0.11.x 依赖 Bootstrap SCSS 和 Font-Awesome JS，
这些文件在 node_modules 中，需要在 CI 中单独安装主题依赖。

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: kevinten10

.github/workflows/deploy.yml

@@ -31,9 +31,12 @@ jobs:
           node-version: '20'
           cache: 'npm'
 
-      - name: "Install dependencies"
+      - name: "Install project dependencies"
         run: npm ci
 
+      - name: "Install Docsy theme dependencies"
+        run: cd themes/docsy && npm install
+
       - name: "Create Hugo module directories for Docsy"
         run: node themes/docsy/tools/mkdirp-hugo-mod.js themes