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

QUICKSTART.md

@@ -37,7 +37,7 @@ nano backend/.env
 
 Vérifiez:
 ```env
-PORT=3000
+PORT=4001
 SERVER_DIR=/home/innotex/Documents/Projet/Serveur NationsGlory/NationsGlory_ServeurBuild_Red
 RCON_HOST=localhost
 RCON_PORT=25575
@@ -51,12 +51,12 @@ RCON_PORT=25575
 
 Vous devriez voir:
 ```
-🚀 Backend Admin NationsGlory démarré sur http://localhost:3000
+🚀 Backend Admin NationsGlory démarré sur http://localhost:4001
 ```
 
 ### 5️⃣ Accès (10 secondes)
 
-Ouvrez: **http://localhost:3000**
+Ouvrez: **http://localhost:4001**
 
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