fix(deps): update dependency org.flywaydb:flyway-core to v12

Author: renovate[bot]

backend/build.gradle.kts

@@ -50,7 +50,7 @@ dependencies {
     implementation("org.ehcache:ehcache:3.11.1")
 
     // Run Flyway DB migration tool on startup https://flywaydb.org/
-    implementation("org.flywaydb:flyway-core:8.5.13")
+    implementation("org.flywaydb:flyway-core:12.0.0")
 
     // Read .mmdb (MaxMind) DB files for IP lookups https://maxmind.github.io/MaxMind-DB/
     implementation("com.maxmind.geoip2:geoip2:4.4.0")