chore: Path-specific rules 추가

- 관련 파일 작업 시에만 로드되도록

Author: whqtker

.claude/rules/code-style.md

@@ -1,3 +1,8 @@
+---
+paths:
+  - "src/**/*.java"
+---
+
 # Code Style
 
 ## Naming

.claude/rules/database.md

@@ -1,3 +1,9 @@
+---
+paths:
+  - "src/main/java/**/domain/*.java"
+  - "src/main/resources/db/migration/*.sql"
+---
+
 # Database
 
 ## JPA Entity

.claude/rules/testing.md

@@ -1,3 +1,8 @@
+---
+paths:
+  - "src/test/**/*.java"
+---
+
 # Testing
 
 Base annotation: `@TestContainerSpringBootTest` for all integration tests.