refactor(domain-manager): simplify frontend URL configuration (#10194)

Replaced multiple environment variables for frontend URL construction
with a single FRONTEND_URL variable. This change reduces complexity and
improves clarity by consolidating frontend URL handling into one source.
Updated relevant validations and removed unused variables like
FRONT_PROTOCOL and FRONT_PORT.

Fix #10016

packages/twenty-docker/docker-compose.yml

@@ -20,7 +20,7 @@ services:
     ports:
       - "3000:3000"
     environment:
-      PORT: 3000
+      NODE_PORT: 3000
       PG_DATABASE_URL: postgres://${PG_DATABASE_USER:-postgres}:${PG_DATABASE_PASSWORD:-postgres}@${PG_DATABASE_HOST:-db}:${PG_DATABASE_PORT:-5432}/default
       SERVER_URL: ${SERVER_URL}
       REDIS_URL: ${REDIS_URL:-redis://redis:6379}