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/ViewModels/ProgressViewModel.swift

@@ -108,6 +108,12 @@ final class ProgressViewModel {
         leagueProgress.stadiumsRemaining
     }
 
+    /// Count of trips for the selected sport (stub - can be enhanced)
+    var tripCount: Int {
+        // TODO: Fetch saved trips count from SwiftData
+        0
+    }
+
     /// Recent visits sorted by date
     var recentVisits: [VisitSummary] {
         visits

SportsTime/Features/Progress/Views/AchievementsListView.swift

@@ -36,6 +36,20 @@ struct AchievementsListView: View {
         }
         .themedBackground()
         .navigationTitle("Achievements")
+        .toolbar {
+            ToolbarItem(placement: .topBarTrailing) {
+                if !earnedAchievements.isEmpty {
+                    ShareButton(
+                        content: AchievementCollectionContent(
+                            achievements: earnedAchievements,
+                            year: Calendar.current.component(.year, from: Date())
+                        ),
+                        style: .icon
+                    )
+                    .foregroundStyle(Theme.warmOrange)
+                }
+            }
+        }
         .task {
             await loadAchievements()
         }
@@ -184,6 +198,10 @@ struct AchievementsListView: View {
         }
     }
 
+    private var earnedAchievements: [AchievementProgress] {
+        achievements.filter { $0.isEarned }
+    }
+
     private var filteredAchievements: [AchievementProgress] {
         let filtered: [AchievementProgress]
 

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