feat(security): Enhance email obfuscation

- Install and enable 'jekyll-email-protect' plugin
- Configure plugin in _config.yml (plugins and whitelist)
- Obfuscate email in _includes/sidebar.html using encode_email filter in addition to the existing JavaScript-based method for mailto link

Rationale: mitigate email scraping by spam bots while preserving user experience.
Scope: no UI changes beyond obfuscated mailto; build requires bundler to include the new gem.

Author: yunseo-kim

Gemfile

@@ -16,4 +16,5 @@ gem "wdm", "~> 0.2.0", :platforms => [:mingw, :x64_mingw, :mswin]
 group :jekyll_plugins do
   gem 'jekyll-polyglot'
   gem 'jekyll-redirect-from'
+  gem 'jekyll-email-protect'
 end

_config.yml

@@ -266,7 +266,11 @@ jekyll-archives:
     category: /categories/:name/
 
 plugins:
+  - jekyll-polyglot
   - jekyll-redirect-from
+  - jekyll-email-protect
 
 whitelist:
+  - jekyll-polyglot
   - jekyll-redirect-from
+  - jekyll-email-protect

_includes/sidebar.html

@@ -63,9 +63,9 @@
             https://{{ entry.type }}.com/{{ site[entry.type].username }}
           {%- endcapture -%}
         {% when 'email' %}
-          {% assign email = site.social.email | split: '@' %}
+          {% assign obfs_email = site.social.email | encode_email | split: '@' %}
           {%- capture url -%}
-            javascript:location.href = 'mailto:' + ['{{ email[0] }}','{{ email[1] }}'].join('@')
+            javascript:location.href = 'mailto:' + ['{{ obfs_email[0] }}','{{ obfs_email[1] }}'].join('@')
           {%- endcapture -%}
         {% when 'rss' %}
           {% assign url = '/feed.xml' | relative_url %}