Fix tvOS memory crash: cap highlights to 50, replace blurs with gradients

The app was crashing from memory pressure on tvOS. Three causes fixed:

1. Feed was rendering all 418 highlights at once — capped to 50 items.

2. FeaturedGameCard had 3 blur effects (radius 80-120) on large circles
   for team color glow — replaced with a single LinearGradient. Same
   visual effect, fraction of the GPU memory.

3. BroadcastBackground had 3 blurred circles (radius 120-140, 680-900px)
   rendering on every screen — replaced with RadialGradients which are
   composited by the GPU natively without offscreen render passes.

Also fixed iOS build: replaced tvOS-only font refs (tvSectionTitle,
tvBody) with cross-platform equivalents in DashboardView fallback state.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

mlbTVOS/Views/Components/ScoresTickerView.swift

@@ -19,10 +19,10 @@ struct ScoresTickerView: View {
                 .padding(.vertical, 14)
                 .background(
                     RoundedRectangle(cornerRadius: 18, style: .continuous)
-                        .fill(.black.opacity(0.72))
+                        .fill(DS.Colors.navFill)
                         .overlay {
                             RoundedRectangle(cornerRadius: 18, style: .continuous)
-                                .strokeBorder(.white.opacity(0.08), lineWidth: 1)
+                                .strokeBorder(DS.Colors.panelStroke, lineWidth: 1)
                         }
                 )
                 .accessibilityHidden(true)