Redesign achievements progress bar with milestone circles

Replaces the simple progress bar with a custom milestone bar showing
individual circles for each achievement, filled when unlocked with a
checkmark indicator.

Fixes #27

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

PortfolioJournal/Views/Dashboard/MonthlyCheckInView.swift

@@ -705,18 +705,18 @@ struct AchievementsView: View {
     private var headerCard: some View {
         let total = max(achievementStatuses.count, 1)
         let unlockedCount = unlockedAchievements.count
-        let progress = Double(unlockedCount) / Double(total)
 
         return VStack(alignment: .leading, spacing: 8) {
             Text(String(localized: "achievements_progress_title"))
                 .font(.headline)
-            ProgressView(value: progress)
-                .tint(.appSecondary)
+
+            AchievementMilestoneBar(statuses: achievementStatuses)
+
             Text(
                 String(
                     format: NSLocalizedString("achievements_unlocked_count", comment: ""),
                     unlockedCount,
-                    achievementStatuses.count
+                    total
                 )
             )
                 .font(.subheadline)
@@ -833,6 +833,61 @@ private extension MonthlyCheckInView {
 
 }
 
+// MARK: - Achievement Milestone Bar
+
+struct AchievementMilestoneBar: View {
+    let statuses: [MonthlyCheckInAchievementStatus]
+
+    var body: some View {
+        let total = max(statuses.count, 1)
+        let unlockedCount = statuses.filter(\.isUnlocked).count
+        let progress = Double(unlockedCount) / Double(total)
+
+        GeometryReader { geo in
+            let barWidth = geo.size.width
+            let barHeight: CGFloat = 6
+
+            ZStack(alignment: .leading) {
+                // Background track
+                Capsule()
+                    .fill(Color.gray.opacity(0.2))
+                    .frame(height: barHeight)
+
+                // Filled track
+                Capsule()
+                    .fill(Color.appSecondary)
+                    .frame(width: barWidth * progress, height: barHeight)
+
+                // Milestone circles
+                ForEach(Array(statuses.enumerated()), id: \.element.id) { index, status in
+                    let position = total == 1
+                        ? barWidth / 2
+                        : barWidth * Double(index) / Double(total - 1)
+
+                    Circle()
+                        .fill(status.isUnlocked ? Color.appSecondary : Color.gray.opacity(0.3))
+                        .frame(width: 14, height: 14)
+                        .overlay(
+                            Circle()
+                                .stroke(Color(.systemBackground), lineWidth: 2)
+                        )
+                        .overlay(
+                            Group {
+                                if status.isUnlocked {
+                                    Image(systemName: "checkmark")
+                                        .font(.system(size: 7, weight: .bold))
+                                        .foregroundColor(.white)
+                                }
+                            }
+                        )
+                        .position(x: position, y: geo.size.height / 2)
+                }
+            }
+        }
+        .frame(height: 20)
+    }
+}
+
 #Preview {
     NavigationStack {
         MonthlyCheckInView()