feat: per-operator filter in the statistics dashboard

New Operator picker next to the contest picker, populated with the operators
actually present in the log. Selecting one recomputes every statistic for that
operator — QSO/DXCC totals, top countries, continent split, by band/mode, and
the rate/best-60. "— Station owner —" buckets QSOs logged with no OPERATOR set.
Shown only when the log has more than one operator.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

frontend/wailsjs/go/main/App.d.ts

@@ -356,7 +356,7 @@ export function GetLoTWUsersStatus():Promise<main.LoTWUsersStatus>;
 
 export function GetLogFilePath():Promise<string>;
 
-export function GetLogStats(arg1:string,arg2:string,arg3:string,arg4:number):Promise<qso.Stats>;
+export function GetLogStats(arg1:string,arg2:string,arg3:string,arg4:number,arg5:string):Promise<qso.Stats>;
 
 export function GetLogbookRevision():Promise<string>;
 
@@ -368,6 +368,8 @@ export function GetOfflineStatus():Promise<main.OfflineStatus>;
 
 export function GetOnlineOperators():Promise<Array<main.ChatPresence>>;
 
+export function GetOperators():Promise<Array<string>>;
+
 export function GetPGXLSettings():Promise<main.PGXLSettings>;
 
 export function GetPGXLStatus():Promise<powergenius.Status>;