chore: AI 가이드라인 제거 (#158)

- Junie, Cursor, GitHub Copilot 가이드라인을 추적하지 않도록 설정

Author: jayn2u

.gitignore

@@ -51,4 +51,13 @@ application-prod.yml
 /eat-ssu.tar
 
 ### SDKMAN ###
-.sdkmanrc
+.sdkmanrc
+
+### Junie guideline ###
+.junie
+
+### Cursor guideline ###
+eatssu-server-rule.mdc
+
+### Copilot guildline ###
+copilot-instructions.md