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/database/model/model.go

@@ -525,18 +525,6 @@ type NodeSummary struct {
 	XrayError string `json:"xrayError,omitempty"`
 }
 
-type CustomGeoResource struct {
-	Id            int    `json:"id" gorm:"primaryKey;autoIncrement"`
-	Type          string `json:"type" gorm:"not null;uniqueIndex:idx_custom_geo_type_alias;column:geo_type"`
-	Alias         string `json:"alias" gorm:"not null;uniqueIndex:idx_custom_geo_type_alias"`
-	Url           string `json:"url" gorm:"not null"`
-	LocalPath     string `json:"localPath" gorm:"column:local_path"`
-	LastUpdatedAt int64  `json:"lastUpdatedAt" gorm:"default:0;column:last_updated_at"`
-	LastModified  string `json:"lastModified" gorm:"column:last_modified"`
-	CreatedAt     int64  `json:"createdAt" gorm:"autoCreateTime:milli;column:created_at"`
-	UpdatedAt     int64  `json:"updatedAt" gorm:"autoUpdateTime:milli;column:updated_at"`
-}
-
 type ClientReverse struct {
 	Tag string `json:"tag"`
 }