feat: migrate application port from 3000 to 4001 and fix circular dependencies

- Change default port to 4001 across all configuration files (server.js, docker-compose.yml, .env, Dockerfile)
- Update frontend API URL to use new port 4001
- Fix circular dependency issues in route files by using process.env.SERVER_DIR instead of importing from server.js
- Apply to all routes: auth.js, backup.js, logs.js, players.js, rcon.js, server.js, whitelist.js
- Fix environment variable loading in start.sh to properly handle paths with spaces
- Quote SERVER_DIR path in .env to preserve spaces in directory paths
- Update all documentation references from port 3000 to 4001 (README, QUICKSTART, CONFIGURATION, INDEX)
- Remove debug console.log statements from auth.js
- Remove test utility file test-ops.js

Fixes: Port conflict issues, circular dependency warnings, environment variable parsing

INDEX.md

@@ -66,7 +66,7 @@ WebNationsGlory_ServeurBuild_Red/
 3. Éditer les fichiers .env
 
 ### Pour Utiliser l'Application
-1. Ouvrir http://localhost:3000
+1. Ouvrir http://localhost:4001
 2. Créer le compte admin
 3. Utiliser les onglets du dashboard
 
@@ -117,7 +117,7 @@ nano backend/.env
 ./start.sh
 
 # 5. Accès
-# Ouvrir: http://localhost:3000
+# Ouvrir: http://localhost:4001
 ```
 
 ## 📚 Fichiers Importants à Connaître