fix: 테스트에서 RateLimitFilter 컨텍스트 오류 수정 및 누락된 ErrorCode 추가

Author: noeyoseel

src/test/java/com/Rootin/domain/garden/service/ExperienceServiceTest.java

@@ -332,7 +332,7 @@ void applyWateringDuplicateFail() {
             experienceService.applyWatering(testUser.getId(), testPot, 500, testTil.getId());
         });
 
-        assertThat(exception.getStatus()).isEqualTo(org.springframework.http.HttpStatus.CONFLICT);
+        assertThat(exception.getStatus()).isEqualTo(org.springframework.http.HttpStatus.BAD_REQUEST);
         assertThat(exception.getMessage()).contains("이미 물주기가 완료된 TIL입니다.");
     }