Update API URL configuration format.

Consolidate API URL settings by merging separate base, prefix, and version variables into a single backend URL. This change simplifies the API configuration process and ensures consistency across documentation. Make sure there are no trailing slashes and the correct protocol (http or https) is used.

Author: Gamer-VII

Writerside/topics/gml-faq.md

@@ -25,9 +25,7 @@
   следующим образом
     ```
     # Адрес к Web Api
-    NEXT_PUBLIC_BASE_URL=http://localhost:5000
-    NEXT_PUBLIC_PREFIX_API=api
-    NEXT_PUBLIC_VERSION_API=v1
+    NEXT_PUBLIC_BACKEND_URL=http://localhost:5000/api/v1
     ```
   > Внимание! Не должно быть ```/``` в конце адреса и выбран верный протокол ```http``` или ```https```
 

Writerside/topics/server-install-from-source.md

@@ -88,9 +88,7 @@ SERVICE_TEXTURE_ENDPOINT=http://gml-web-skins:8085
 
 ```yaml
  # Адрес к Web Api
-NEXT_PUBLIC_BASE_URL=http://localhost:5000
-NEXT_PUBLIC_PREFIX_API=api
-NEXT_PUBLIC_VERSION_API=v1
+ NEXT_PUBLIC_BACKEND_URL=http://localhost:5000/api/v1
 ```
 
 #### Шаг 5: Запуск проекта с использованием Docker