feat(infra) : ajout maintenance mode dans nginx-proxy

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

infra/prod/nginx-proxy.conf

@@ -3,8 +3,25 @@ server {
     listen [::]:80;
     server_name project.malio-dev.fr;
 
+    root /var/www/lesstime;
+
+    # Maintenance mode
+    if (-f /var/www/lesstime/maintenance.on) {
+        return 503;
+    }
+
+    error_page 503 @maintenance;
+
+    location @maintenance {
+        rewrite ^(.*)$ /maintenance.html break;
+    }
+
+    location = /maintenance.html {
+        internal;
+    }
+
     location / {
-        proxy_pass http://127.0.0.1:8080;
+        proxy_pass http://127.0.0.1:8081;
         proxy_set_header Host $host;
         proxy_set_header X-Real-IP $remote_addr;
         proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;