refactor: rename 'allow_change_password' to 'allow_modify_login_info' and update related logic across the application

src/langbot/templates/config.yaml

@@ -16,7 +16,7 @@ proxy:
     https: ''
 system:
     recovery_key: ''
-    allow_change_password: true
+    allow_modify_login_info: true
     jwt:
         expire: 604800
         secret: ''
@@ -75,6 +75,6 @@ space:
     # Space service URL for OAuth and API
     url: 'https://space.langbot.app'
     # Space API URL for model requests (MaaS)
-    api_url: 'https://api.langbot.app'
+    models_gateway_api_url: 'https://api.langbot.cloud'
     # OAuth authorization page URL (user will be redirected here)
     oauth_authorize_url: 'https://space.langbot.app/auth/authorize'