feat: relay auto-control by frequency / band (PstRotator-style)

Automatically switches the Station Control relay boards from the rig's
current frequency / band. Each relay carries one rule: off (manual), a
frequency window (ON inside [lo,hi] kHz, OFF outside), or a set of bands
(ON on those bands, OFF elsewhere). Evaluated on every CAT frequency/band
change; a relay is only switched when its desired state actually changed,
so tuning within a range doesn't hammer the board.

A cached atomic flag keeps the CAT hot path a no-op when the feature is off
(important during FT8 slice churn). Saving re-applies from the live
frequency so a changed rule takes effect immediately.

New Settings → Hardware → Relay auto-control section: master enable plus a
per-relay mode (Off / Frequency / Band) with kHz range inputs or band
chips, per configured relay board. i18n EN + FR. Azimuth/Time modes (the
other two PstRotator tabs) are left for later.

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

@@ -386,6 +386,8 @@ export function GetQSO(arg1:number):Promise<qso.QSO>;
 
 export function GetQSORate():Promise<main.QSORate>;
 
+export function GetRelayAuto():Promise<main.RelayAutoConfig>;
+
 export function GetRotatorHeading():Promise<main.RotatorHeading>;
 
 export function GetRotatorSettings():Promise<main.RotatorSettings>;
@@ -740,6 +742,8 @@ export function SaveProfile(arg1:profile.Profile):Promise<profile.Profile>;
 
 export function SaveQSLDefaults(arg1:main.QSLDefaults):Promise<void>;
 
+export function SaveRelayAuto(arg1:main.RelayAutoConfig):Promise<void>;
+
 export function SaveRotatorSettings(arg1:main.RotatorSettings):Promise<void>;
 
 export function SaveStationDevices(arg1:Array<main.StationDevice>):Promise<void>;