chore: Bump com.github.spotbugs from 6.0.18 to 6.0.19 in /backend

Bumps com.github.spotbugs from 6.0.18 to 6.0.19.

---
updated-dependencies:
- dependency-name: com.github.spotbugs
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

backend/build.gradle

@@ -4,7 +4,7 @@ plugins {
     id "org.springframework.boot" version "3.3.1"
     id "io.spring.dependency-management" version "1.1.6"
     id "io.freefair.lombok" version "8.6"
-    id "com.github.spotbugs" version "6.0.18"
+    id "com.github.spotbugs" version "6.0.19"
     id "com.github.ben-manes.versions" version "0.51.0"
     id "org.owasp.dependencycheck" version "8.4.3"
     id "com.diffplug.spotless" version "6.25.0"