[Tech] Bump org.flywaydb:flyway-core from 10.21.0 to 11.1.0 in /backend

Bumps [org.flywaydb:flyway-core](https://github.com/flyway/flyway) from 10.21.0 to 11.1.0.
- [Release notes](https://github.com/flyway/flyway/releases)
- [Commits](flyway/flyway@flyway-10.21.0...flyway-11.1.0)

---
updated-dependencies:
- dependency-name: org.flywaydb:flyway-core
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

backend/build.gradle.kts

@@ -64,7 +64,7 @@ dependencies {
     api("jakarta.validation:jakarta.validation-api:3.1.0")
     api("com.fasterxml.jackson.module:jackson-module-kotlin:2.18.2")
     api("com.nhaarman.mockitokotlin2:mockito-kotlin:2.2.0")
-    api("org.flywaydb:flyway-core:10.21.0")
+    api("org.flywaydb:flyway-core:11.1.0")
     api("org.flywaydb:flyway-database-postgresql:10.21.0")
     api("org.springdoc:springdoc-openapi-ui:1.8.0")
     api("org.jetbrains.kotlin:kotlin-reflect:2.0.21")