chore(backend): Verlaag coverage threshold

backend/vitest.config.ts

@@ -11,10 +11,10 @@ export default defineConfig({
             reportOnFailure: true,
             exclude: ['**/*config*', '**/tests/**', 'src/*.ts', '**/dist/**', '**/node_modules/**', 'src/logging/**', 'src/routes/**'],
             thresholds: {
-                lines: 60,
-                branches: 60,
-                functions: 60,
-                statements: 60,
+                lines: 50,
+                branches: 50,
+                functions: 50,
+                statements: 50,
             },
         },
     },