fix(location): update distance reference coordinates

Summary:
- Update the fixed reference longitude and latitude used by distance
  calculation.

Rationale:
- Use the intended location as the distance origin for visitor information.

Tests:
- node --check source/js/custom.js
- git diff --cached --check

Co-authored-by: Codex <codex@openai.com>

Author: windshadow233

source/js/custom.js

@@ -74,7 +74,7 @@ function getDistance(e, t, n, o) {
        success: function(res) {
           let { result = {} } = res
           if(result && result.location) {
-             let distance = getDistance(117.22901, 31.82057, result.location.lng, result.location.lat);
+             let distance = getDistance(120.267609, 30.204311, result.location.lng, result.location.lat);
              setInfo(result.ip, result.ad_info.province + result.ad_info.city + result.ad_info.district, distance, false);
           }
        }