Refa: enlarge default max request body size. (#6088)

### What problem does this PR solve?


### Type of change


- [x] Refactoring

api/apps/__init__.py

 app.config["SESSION_PERMANENT"] = False
 app.config["SESSION_TYPE"] = "filesystem"
 app.config["MAX_CONTENT_LENGTH"] = int(
-    os.environ.get("MAX_CONTENT_LENGTH", 128 * 1024 * 1024)
+    os.environ.get("MAX_CONTENT_LENGTH", 1024 * 1024 * 1024)
 )
 
 Session(app)

docker/nginx/nginx.conf

     keepalive_timeout  65;
 
     #gzip  on;
-    client_max_body_size 128M;
+    client_max_body_size 1024M;
 
     include /etc/nginx/conf.d/ragflow.conf;
 }