feat(sharing): implement unified sharing system for social media

Replace old ProgressCardGenerator with protocol-based sharing architecture
supporting trips, achievements, and stadium progress. Features 8 color
themes, Instagram Stories optimization (1080x1920), and reusable card
components with map snapshots.

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

SportsTime/Features/Progress/Views/ProgressTabView.swift

@@ -15,7 +15,6 @@ struct ProgressTabView: View {
     @State private var viewModel = ProgressViewModel()
     @State private var showVisitSheet = false
     @State private var showPhotoImport = false
-    @State private var showShareSheet = false
     @State private var selectedStadium: Stadium?
     @State private var selectedVisitId: UUID?
 
@@ -65,12 +64,12 @@ struct ProgressTabView: View {
         .themedBackground()
         .toolbar {
             ToolbarItem(placement: .topBarLeading) {
-                Button {
-                    showShareSheet = true
-                } label: {
-                    Image(systemName: "square.and.arrow.up")
-                        .foregroundStyle(Theme.warmOrange)
-                }
+                ShareButton(
+                    progress: viewModel.leagueProgress,
+                    tripCount: viewModel.tripCount,
+                    style: .icon
+                )
+                .foregroundStyle(Theme.warmOrange)
             }
 
             ToolbarItem(placement: .primaryAction) {
@@ -125,9 +124,6 @@ struct ProgressTabView: View {
             )
             .presentationDetents([.medium])
         }
-        .sheet(isPresented: $showShareSheet) {
-            ProgressShareView(progress: viewModel.leagueProgress)
-        }
     }
 
     // MARK: - League Selector