feat: implement Dynamic Type with Apple text styles

Replace all custom Theme.FontSize values and hardcoded font sizes with
Apple's built-in text styles (.largeTitle, .title2, .headline, .body,
.subheadline, .caption, .caption2) to support accessibility scaling.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

SportsTime/Features/Home/Views/LoadingTripsView.swift

@@ -17,7 +17,7 @@ struct LoadingTripsView: View {
             // Header
             HStack {
                 Text("Featured Trips")
-                    .font(.system(size: Theme.FontSize.sectionTitle, weight: .bold, design: .rounded))
+                    .font(.title2)
                     .foregroundStyle(Theme.textPrimary(colorScheme))
                 Spacer()
             }
@@ -27,7 +27,7 @@ struct LoadingTripsView: View {
                 LoadingDots()
 
                 Text(message)
-                    .font(.system(size: Theme.FontSize.body))
+                    .font(.body)
                     .foregroundStyle(Theme.textSecondary(colorScheme))
                     .lineLimit(2)
                     .fixedSize(horizontal: false, vertical: true)