Bump com.google.code.gson:gson from 2.11.0 to 2.12.1 in /backend

Bumps [com.google.code.gson:gson](https://github.com/google/gson) from 2.11.0 to 2.12.1.
- [Release notes](https://github.com/google/gson/releases)
- [Changelog](https://github.com/google/gson/blob/main/CHANGELOG.md)
- [Commits](google/gson@gson-parent-2.11.0...gson-parent-2.12.1)

---
updated-dependencies:
- dependency-name: com.google.code.gson:gson
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

backend/build.gradle.kts

@@ -74,7 +74,7 @@ dependencies {
     implementation("org.flywaydb:flyway-database-postgresql:$flywayVersion")
     implementation("org.postgresql:postgresql:42.7.3")
     implementation("io.ktor:ktor-server-cors:$ktor_version")
-    implementation("com.google.code.gson:gson:2.11.0")
+    implementation("com.google.code.gson:gson:2.12.1")
     implementation("com.azure:azure-identity:1.+")
     implementation("com.microsoft.graph:microsoft-graph:6.16.0")
     implementation("com.github.ben-manes.caffeine:caffeine:3.1.6")