refactor: replace custom geo manager with Xray-core native geodata auto-update

Remove the panel-side custom geo download feature (service, controller,
/panel/api/custom-geo/* endpoints, CustomGeoResource model, UI tab) in
favor of Xray-core's native geodata section
(https://xtls.github.io/config/geodata.html).

- pass the top-level "geodata" key through xray.Config so it survives
  the template round-trip into the generated config
- add a Geodata Auto-Update section to the Xray Updates modal that
  edits geodata (cron schedule, download outbound, asset list) in the
  config template and restarts Xray on save
- previously downloaded geo files in the bin folder keep working in
  ext: routing rules; the orphaned custom_geo_resources table is left
  in place so existing source URLs stay recoverable

internal/web/controller/api_docs_test.go

@@ -99,8 +99,6 @@ func TestAPIRoutesDocumented(t *testing.T) {
 			basePath = "/panel/api/setting"
 		case "xray_setting.go":
 			basePath = "/panel/api/xray"
-		case "custom_geo.go":
-			basePath = "/panel/api/custom-geo"
 		case "websocket.go":
 			basePath = ""
 		}