Bump io.javalin:javalin from 5.6.3 to 6.3.0 in /server

Bumps [io.javalin:javalin](https://github.com/javalin/javalin) from 5.6.3 to 6.3.0.
- [Release notes](https://github.com/javalin/javalin/releases)
- [Commits](javalin/javalin@javalin-parent-5.6.3...javalin-parent-6.3.0)

---
updated-dependencies:
- dependency-name: io.javalin:javalin
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

server/build.gradle

@@ -29,7 +29,7 @@ repositories {
 // External dependencies that our application utilizes
 dependencies {
   // Javalin, a simple web framework for Java
-  implementation 'io.javalin:javalin:5.6.3'
+  implementation 'io.javalin:javalin:6.3.0'
 
   // Jackson, a JSON library for Java
   implementation 'com.fasterxml.jackson.core:jackson-databind:2.17.2'