live activity: remove the white/grey background circle behind the pump

User: 'Remove the white background circle from the live activity'. Drop
the explicit Circle badge and render the fuel-tinted fuelpump.fill on its
own (sized up 19 -> 28 since it no longer sits inside a disc).

FuelBoardWidgets/FuelBoardLiveActivityView.swift

@@ -73,15 +73,6 @@ private struct FuelBoardLiveActivityView: View {
     /// "ideal" width past the iPhone Lock Screen and collapses the full card).
     private let compactWidthThreshold: CGFloat = 280
 
-    /// The badge circle behind the pump. The user calls this "the white
-    /// circle" and wants it slightly darkened for contrast against the bright
-    /// fuel pump. Built as an explicit grey disc (the light-grey "white circle
-    /// darker") — NOT part of the SF Symbol glyph, so it can never swallow the
-    /// darkened colour the way `fuelpump.circle.fill` did.
-    private var badgeCircleColor: Color {
-        Color(white: 0.86)
-    }
-
     var body: some View {
         Link(destination: context.state.mapsURL) {
             GeometryReader { geo in
@@ -108,19 +99,11 @@ private struct FuelBoardLiveActivityView: View {
     /// Full three-column design (unchanged): brand glyph · fuel+station · price.
     private var richBody: some View {
         HStack(spacing: 12) {
-            // LEFT — station brand badge: an explicit darkened circle with a
-            // bright fuel-tinted pump. Built from two shapes so the circle
-            // colour and pump colour are unambiguous (the myth that
-            // fuelpump.circle.fill's first style is the circle is what put the
-            // darkened colour on the pump).
-            ZStack {
-                Circle()
-                    .fill(badgeCircleColor)
-                    .frame(width: 40, height: 40)
+            // LEFT — station brand glyph: the fuel-tinted pump on its own. No
+            // background circle behind it (user request).
             Image(systemName: "fuelpump.fill")
-                    .font(.system(size: 19, weight: .semibold))
+                .font(.system(size: 28, weight: .semibold))
                 .foregroundStyle(context.state.fuel.tintColor)
-            }
                 .frame(width: 40, height: 40)
 
             // MIDDLE — fuel + station