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/Export/Services/ProgressCardGenerator.swift

@@ -410,7 +410,7 @@ struct ProgressShareView: View {
     private var previewCard: some View {
         VStack(spacing: Theme.Spacing.md) {
             Text("Preview")
-                .font(.system(size: Theme.FontSize.caption, weight: .medium))
+                .font(.subheadline)
                 .foregroundStyle(Theme.textMuted(colorScheme))
 
             // Mini preview
@@ -486,7 +486,7 @@ struct ProgressShareView: View {
             // Style selector
             VStack(alignment: .leading, spacing: Theme.Spacing.xs) {
                 Text("Style")
-                    .font(.system(size: Theme.FontSize.caption, weight: .medium))
+                    .font(.subheadline)
                     .foregroundStyle(Theme.textMuted(colorScheme))
 
                 HStack(spacing: Theme.Spacing.sm) {
@@ -499,7 +499,7 @@ struct ProgressShareView: View {
             // Username toggle
             Toggle(isOn: $includeUsername) {
                 Text("Include Username")
-                    .font(.system(size: Theme.FontSize.body))
+                    .font(.body)
             }
             .padding(.horizontal)
 
@@ -512,7 +512,7 @@ struct ProgressShareView: View {
             // Map toggle
             Toggle(isOn: $includeMap) {
                 Text("Include Map")
-                    .font(.system(size: Theme.FontSize.body))
+                    .font(.body)
             }
             .padding(.horizontal)
         }
@@ -525,7 +525,7 @@ struct ProgressShareView: View {
             withAnimation { cardStyle = style }
         } label: {
             Text(label)
-                .font(.system(size: Theme.FontSize.caption, weight: .medium))
+                .font(.subheadline)
                 .foregroundStyle(cardStyle == style ? .white : Theme.textPrimary(colorScheme))
                 .padding(.horizontal, Theme.Spacing.md)
                 .padding(.vertical, Theme.Spacing.sm)