fix(deps): update dependency org.junit:junit-bom to v6 (#348)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

backend/build.gradle

@@ -29,7 +29,7 @@ dependencies {
 
 	testCompileOnly 'org.projectlombok:lombok:1.18.42'
 	testAnnotationProcessor 'org.projectlombok:lombok:1.18.42'
-	testImplementation platform('org.junit:junit-bom:5.14.3')
+	testImplementation platform('org.junit:junit-bom:6.0.3')
 	testImplementation 'org.junit.jupiter:junit-jupiter'
 	testImplementation 'io.projectreactor:reactor-test' // Add this for StepVerifier