fix(settings): move content padding inside scroll areas to keep inner borders visible

The settings shell wrapped children in an outer section with p-3/p-4 padding.
With OverlayScrollbars replacing native scroll, the overlay scrollbar sat at
the viewport's right edge and covered the right border of inner cards.

Drop the outer padding (and the now-redundant overflow-auto) from the shell
and apply p-3 md:p-4 inside each settings page instead, so the scrollbar
aligns with the column edge while inner sections stay within the padded area.

src/components/settings/settings-shell.tsx

@@ -236,12 +236,7 @@ export function SettingsShell({ children }: SettingsShellProps) {
           </Sheet>
         )}
 
-        <section
-          className={cn(
-            "flex-1 min-w-0 min-h-0 overflow-auto",
-            isMobile ? "p-3" : "p-4"
-          )}
-        >
+        <section className="flex-1 min-w-0 min-h-0 overflow-hidden">
           {children}
         </section>
       </div>