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

README.md

@@ -81,7 +81,7 @@ chmod +x install.sh
 Éditer `backend/.env`:
 ```env
 NODE_ENV=development
-PORT=3000
+PORT=4001
 SESSION_SECRET=changez-cette-cle-en-production
 SERVER_DIR=/path/to/NationsGlory_ServeurBuild_Red
 RCON_HOST=localhost
@@ -95,11 +95,11 @@ chmod +x start.sh
 ./start.sh
 ```
 
-L'interface est maintenant accessible sur: **http://localhost:3000**
+L'interface est maintenant accessible sur: **http://localhost:4001**
 
 ## 🎯 Premier Démarrage
 
-1. Ouvrez http://localhost:3000
+1. Ouvrez http://localhost:4001
 2. Créez le compte admin (doit être un OP du serveur)
 3. Connectez-vous
 4. Explorez l'interface!