docs: adjust documentation to reflect single-binary deployments

docs/nginx.conf

@@ -22,4 +22,9 @@ server {
     location /docs/docs {
         return 301 $scheme://vikunja.io/docs;
     }
+    
+    location /docs {
+        rewrite ^/docs/install-backend/?$ /docs/install redirect;
+        rewrite ^/docs/install-frontend/?$ /docs/install redirect;
+    }
 }