live activity: centre content vertically + darken pump circle

A GeometryReader hands its content the full proposed frame and pins it
top-left, so the Lock Screen card sat high instead of vertically centred
when the activity container offered extra height. Wrap the branch in
.frame(maxWidth:.infinity, maxHeight:.infinity, alignment:.center).

Also darken the pump circle to 82% of the raw fuel tint (mix 18% black) so
the white pump symbol keeps contrast against bright Lock Screen/card, esp.
for the light yellow premium / cyan diesel palette colours.

FuelBoardWidgets/FuelBoardLiveActivityView.swift

@@ -73,6 +73,14 @@ private struct FuelBoardLiveActivityView: View {
     /// "ideal" width past the iPhone Lock Screen and collapses the full card).
     private let compactWidthThreshold: CGFloat = 280
 
+    /// Slightly darkened fuel tint for the pump circle so the white pump
+    /// symbol keeps contrast against the bright Lock Screen / card background
+    /// (the raw palette colours like yellow #FFD60A are too light to sit under
+    /// a white glyph).
+    private var pumpCircleColor: Color {
+        context.state.fuel.tintColor.mix(with: .black, by: 0.18)
+    }
+
     var body: some View {
         Link(destination: context.state.mapsURL) {
             GeometryReader { geo in
@@ -80,11 +88,18 @@ private struct FuelBoardLiveActivityView: View {
                 // full Lock Screen width (>= threshold) → rich card, no matter
                 // how long the station name is. Truly small slots (CarPlay /
                 // Watch) offer much less → compact strip.
-                if geo.size.width >= compactWidthThreshold {
-                    richBody
-                } else {
-                    compactBody
+                Group {
+                    if geo.size.width >= compactWidthThreshold {
+                        richBody
+                    } else {
+                        compactBody
+                    }
                 }
+                // A GeometryReader hands its content the FULL proposed frame
+                // (content is otherwise pinned top-left), so centre the card
+                // within that space — keeps the Lock Screen content vertically
+                // aligned instead of sitting high.
+                .frame(maxWidth: .infinity, maxHeight: .infinity, alignment: .center)
             }
         }
     }
@@ -95,7 +110,7 @@ private struct FuelBoardLiveActivityView: View {
             // LEFT — station brand glyph
             Image(systemName: "fuelpump.circle.fill")
                 .font(.system(size: 32))
-                .foregroundStyle(context.state.fuel.tintColor, .white)
+                .foregroundStyle(pumpCircleColor, .white)
                 .frame(width: 40, height: 40)
 
             // MIDDLE — fuel + station