Update LinkedIn profile URL

- Fix LinkedIn username from kevinpark to realcoding
- Update both _config.yml and about.md with correct LinkedIn URL
- LinkedIn profile: https://www.linkedin.com/in/realcoding/

Author: realcoding2003

_config.yml

@@ -9,7 +9,7 @@ author:
   name: Kevin Park
   email: kevinpark@okyc.kr
   github: realcoding2003
-  linkedin: kevinpark
+  linkedin: realcoding
 
 # Build settings
 markdown: kramdown
@@ -56,7 +56,7 @@ paginate_path: "/page:num/"
 
 # Social media
 github_username: realcoding2003
-linkedin_username: kevinpark
+linkedin_username: realcoding
 
 # Google Analytics (나중에 설정)
 # google_analytics: G-XXXXXXXXXX

about.md

@@ -58,7 +58,7 @@ permalink: /about/
 
 - **이메일**: kevinpark@okyc.kr
 - **GitHub**: [@realcoding2003](https://github.com/realcoding2003)
-- **LinkedIn**: [Kevin Park](https://linkedin.com/in/kevinpark)
+- **LinkedIn**: [Kevin Park](https://www.linkedin.com/in/realcoding/)
 
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