fix(deps): Remove spring-session-data-redis dependency

Spring Session conflicts with JWT-based stateless authentication.
The SessionRepositoryFilter was attempting to save sessions to Redis
even with SessionCreationPolicy.STATELESS, causing IllegalStateException
during OAuth2 login.

Changes:
- Remove spring-session-data-redis dependency
- Keep spring-boot-starter-data-redis for caching only
- Redis now used exclusively for:
  * Refresh token storage
  * Access token blacklist
  * General caching

Fixes: Session was invalidated error after OAuth2 login

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

Author: JIWONKIMS

build.gradle.kts

@@ -58,9 +58,8 @@ dependencies {
     implementation("org.springframework.boot:spring-boot-starter-websocket")
     implementation("org.springframework.boot:spring-boot-starter-amqp")
 
-    // 레디스 - 캐싱 및 세션 관리
+    // 레디스 - 캐싱 전용 (JWT 기반 인증으로 세션 불필요)
     implementation("org.springframework.boot:spring-boot-starter-data-redis")
-    implementation("org.springframework.session:spring-session-data-redis")
 
     // API 문서화 - Swagger UI
     implementation("org.springdoc:springdoc-openapi-starter-webmvc-ui:2.7.0")