feat(grids): the square map filters by mode, band and satellite

The FTx button is gone. It was the wrong grain in both directions: the
Digital class already sat a contest RTTY square next to an FT8 one, and
FTx then sat FT8 next to FT4, when what this map answers is where ONE
mode has been heard. The four classes stay as buttons and a dropdown
beside them offers a single mode.

Its contents come from the log, not from a list in the code. That is
what settles FT2: it is not a registered ADIF mode yet, so a hardcoded
list meant either leaving out the operators already using it or shipping
a mode that does not officially exist. A query does neither, and needs
no change here the day it is registered. The mode offered is the SUBMODE
where there is one, because ADIF files PSK63 under PSK and "PSK" is not
the name anybody is looking for.

The band list is the station's own, unioned with anything worked outside
it so nothing in the log is unreachable, ordered by frequency through
the band plan's index — sorting the names puts 10m between 1.25m and
12m. The satellite list is drawn from SAT_NAME on the squares
themselves and the control is absent altogether on a terrestrial log: a
VHF square worked through AO-91 and one worked line-of-sight are not the
same achievement, and until now nothing separated them.

The mode dropdown shares the scope with the class buttons rather than
narrowing on top of them — mode is one question, and two controls both
answering it is how a map ends up showing PHONE ∩ FT8 and nothing else.
A stored FTX preference is read as Digital, so it cannot leave the map
filtered by something no control shows as selected.

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

@@ -685,7 +685,9 @@ export function GetYaesuBandAntennas():Promise<Record<string, number>>;
 
 export function GetYaesuState():Promise<cat.YaesuTXState>;
 
-export function GridSquares(arg1:string):Promise<Array<qso.GridSquare>>;
+export function GridSquareChoices():Promise<main.GridSquareChoices>;
+
+export function GridSquares(arg1:string,arg2:string,arg3:string):Promise<Array<qso.GridSquare>>;
 
 export function HaltAutoCall():Promise<void>;