chore(backend): bump Spring 3.4 -> 3.5 (#1141)

Author: fengelniederhammer

backend/build.gradle.kts

@@ -4,7 +4,7 @@ import java.io.ByteArrayOutputStream
 plugins {
     kotlin("jvm") version "2.3.20"
     kotlin("plugin.spring") version "2.3.20"
-    id("org.springframework.boot") version "3.4.0"
+    id("org.springframework.boot") version "3.5.13"
     id("io.spring.dependency-management") version "1.1.7"
     id("org.jlleitschuh.gradle.ktlint") version "14.2.0"
     id("org.springdoc.openapi-gradle-plugin") version "1.9.0"
@@ -28,7 +28,7 @@ dependencies {
     implementation("org.jetbrains.kotlin:kotlin-reflect")
     implementation("io.github.microutils:kotlin-logging-jvm:3.0.5")
     implementation("org.jetbrains.kotlin:kotlin-stdlib")
-    implementation("org.springdoc:springdoc-openapi-starter-webmvc-ui:2.7.0")
+    implementation("org.springdoc:springdoc-openapi-starter-webmvc-ui:2.8.6")
     implementation("org.flywaydb:flyway-database-postgresql:11.0.0")
     implementation("org.postgresql:postgresql:42.7.10")
     implementation("org.jetbrains.exposed:exposed-spring-boot-starter:1.2.0")