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/xray/config.go

@@ -23,6 +23,7 @@ type Config struct {
 	Observatory      json_util.RawMessage `json:"observatory,omitempty"`
 	BurstObservatory json_util.RawMessage `json:"burstObservatory,omitempty"`
 	Metrics          json_util.RawMessage `json:"metrics"`
+	Geodata          json_util.RawMessage `json:"geodata,omitempty"`
 }
 
 // Equals compares two Config instances for deep equality.
@@ -68,5 +69,8 @@ func (c *Config) Equals(other *Config) bool {
 	if !bytes.Equal(c.Metrics, other.Metrics) {
 		return false
 	}
+	if !bytes.Equal(c.Geodata, other.Geodata) {
+		return false
+	}
 	return true
 }