feat: separate column layout for Recent QSOs in the Main tab

The Main-tab pane and the full Recent QSOs tab are the same component sharing
one storage key, but the pane is about half as wide — so it wants fewer and
narrower columns. Whichever was opened last rewrote the other's widths.

The pane now stores under "mainpane", which also scopes its award-column
visibility and widths. The full tab keeps the historical key, so its layout is
untouched; the pane starts from defaults once.

frontend/src/App.tsx

@@ -4200,6 +4200,11 @@ export default function App() {
           <div className="h-full w-full min-h-0 flex flex-col bg-card border border-border rounded-lg overflow-hidden">
             <RecentQSOsGrid
               key={`rqg-${activeProfileId ?? 'x'}`}
+              // Its OWN layout, separate from the full-width Recent QSOs tab.
+              // This pane is roughly half as wide, so it wants fewer columns and
+              // narrower ones; sharing one key meant whichever was opened last
+              // rewrote the other's widths.
+              storageKey="mainpane"
               rows={qsosWithAwards as any}
               myGrid={station.my_grid}
               total={total}