Update gradle to v2

renovate[bot] · web-flow · commit ab3c457da1b1 · 2025-10-23T14:08:16.000Z
diff --git a/backend/gradle/libs.versions.toml b/backend/gradle/libs.versions.toml
@@ -1,6 +1,6 @@
 [versions]
-kotlin = "1.9.21"
-spring = "1.9.21"
+kotlin = "2.2.21"
+spring = "2.2.21"
 springBoot = "3.2.0"
 springDependencyManagement = "1.1.4"
 
