feat: ClubLog Most Wanted rank in the entry band matrix

Opt-in (Settings → General). Shows a "MW #rank" pill next to the DXCC entity
name in the entry-strip band/slot matrix — ClubLog's Most Wanted ranking
(1 = most wanted), personalised to the operator's callsign and refreshed daily.

- internal/clublog/mostwanted.go: fetch mostwanted.php?api=1&callsign=<CALL>
  (rank→DXCC JSON, real User-Agent), invert to dxcc→rank, cache to
  <dataDir>/clublog_mostwanted.json; NeedsRefresh invalidates on callsign change.
- app.go: keyClublogMostWanted setting, a.clublogMW, startup refresh goroutine,
  activeCallsign() helper, and Get/Set/Download bindings mirroring the cty ones.
  WorkedBefore now carries MWRank (qso.WorkedBefore.MWRank) when enabled.
- BandSlotGrid.tsx: MW pill next to the entity name, colour-tiered by rank.
- SettingsModal General: toggle + download button + status, mirroring the
  ClubLog cty-exceptions block.

Also reorganises the changelog: the theme-persistence fix (landed after the
v0.20.11 tag) plus this feature go under a new 0.20.12 entry; 0.20.11 keeps only
what shipped in its binary.

frontend/src/components/BandSlotGrid.tsx

@@ -94,6 +94,7 @@ export function BandSlotGrid({ wb, busy, currentBand, currentMode, bands, hasCal
   const dxcc = wb?.dxcc ?? 0;
   const dxccName = wb?.dxcc_name ?? '';
   const dxccCount = wb?.dxcc_count ?? 0;
+  const mwRank = wb?.mw_rank ?? 0; // ClubLog Most Wanted rank (1 = most wanted; 0 = off/unknown)
   const callCount = wb?.count ?? 0; // QSOs with this exact callsign
   const hasDxcc = dxcc > 0;
   const newOne = hasDxcc && dxccCount === 0;
@@ -136,6 +137,20 @@ export function BandSlotGrid({ wb, busy, currentBand, currentMode, bands, hasCal
   const newMode = slotNew && bandWorked && !modeWorked;
   const newSlot = slotNew && bandWorked && modeWorked;
 
+  // ClubLog Most Wanted rank pill (shown next to the entity name when the feature
+  // is on). Hotter colour the more wanted the entity is.
+  const mwBadge = mwRank > 0 ? (
+    <Badge
+      title={`ClubLog Most Wanted #${mwRank}`}
+      className={cn('px-1.5 py-0 text-[10px] font-bold shrink-0',
+        mwRank <= 100 ? 'bg-danger text-danger-foreground'
+          : mwRank <= 250 ? 'bg-warning text-warning-foreground'
+            : 'bg-muted text-muted-foreground')}
+    >
+      MW #{mwRank}
+    </Badge>
+  ) : null;
+
   return (
     <section
       className={cn(
@@ -154,12 +169,14 @@ export function BandSlotGrid({ wb, busy, currentBand, currentMode, bands, hasCal
               <strong className="text-warning-muted-foreground font-semibold">{dxccName || `DXCC #${dxcc}`}</strong>
               {' '}· never worked this entity
             </span>
+            {mwBadge}
           </>
         ) : hasDxcc ? (
           <>
             <Badge className="bg-primary text-primary-foreground px-3 py-1 text-xs normal-case font-semibold tracking-normal">
               {dxccName || `DXCC #${dxcc}`}
             </Badge>
+            {mwBadge}
             <span className="text-xs text-muted-foreground">
               <strong className="text-foreground font-semibold">{dxccCount}</strong>{' '}
               QSO{dxccCount > 1 ? 's' : ''} with this entity