🔥(back) remove footer endpoint

With the configuration file, the footer endpoint can be removed and will
not be used anymore by the front application.

src/frontend/apps/e2e/__tests__/app-impress/common.ts

@@ -7,7 +7,6 @@ export const CONFIG = {
   ENVIRONMENT: 'development',
   FRONTEND_CSS_URL: null,
   FRONTEND_HOMEPAGE_FEATURE_ENABLED: true,
-  FRONTEND_FOOTER_FEATURE_ENABLED: true,
   FRONTEND_THEME: 'default',
   MEDIA_BASE_URL: 'http://localhost:8083',
   LANGUAGES: [
@@ -20,6 +19,7 @@ export const CONFIG = {
   LANGUAGE_CODE: 'en-us',
   POSTHOG_KEY: {},
   SENTRY_DSN: null,
+  theme_customization: {},
 };
 
 export const keyCloakSignIn = async (