Add theme picker with 7 color schemes

- Teal: Cool cyan and teal tones (default)
- Orbit: Bold navy and orange
- Retro: Classic columbia blue
- Clutch: Championship red and gold
- Monochrome: Clean grayscale aesthetic
- Sunset: Warm oranges and purples
- Midnight: Deep blues and gold

Features:
- Theme selection persisted via UserDefaults
- ThemeManager singleton for app-wide theme state
- All Theme colors now dynamically switch based on selection
- Settings UI shows color preview circles for each theme

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

SportsTime/Features/Settings/Views/SettingsView.swift

@@ -11,6 +11,9 @@ struct SettingsView: View {
 
     var body: some View {
         List {
+            // Theme Selection
+            themeSection
+
             // Sports Preferences
             sportsSection
 
@@ -37,6 +40,58 @@ struct SettingsView: View {
         }
     }
 
+    // MARK: - Theme Section
+
+    private var themeSection: some View {
+        Section {
+            ForEach(AppTheme.allCases) { theme in
+                Button {
+                    withAnimation(.easeInOut(duration: 0.2)) {
+                        viewModel.selectedTheme = theme
+                    }
+                } label: {
+                    HStack(spacing: 12) {
+                        // Color preview circles
+                        HStack(spacing: -6) {
+                            ForEach(Array(theme.previewColors.enumerated()), id: \.offset) { _, color in
+                                Circle()
+                                    .fill(color)
+                                    .frame(width: 24, height: 24)
+                                    .overlay(
+                                        Circle()
+                                            .stroke(Color.primary.opacity(0.1), lineWidth: 1)
+                                    )
+                            }
+                        }
+
+                        VStack(alignment: .leading, spacing: 2) {
+                            Text(theme.displayName)
+                                .font(.body)
+                                .foregroundStyle(.primary)
+                            Text(theme.description)
+                                .font(.caption)
+                                .foregroundStyle(.secondary)
+                        }
+
+                        Spacer()
+
+                        if viewModel.selectedTheme == theme {
+                            Image(systemName: "checkmark.circle.fill")
+                                .foregroundStyle(Theme.warmOrange)
+                                .font(.title3)
+                        }
+                    }
+                    .contentShape(Rectangle())
+                }
+                .buttonStyle(.plain)
+            }
+        } header: {
+            Text("Theme")
+        } footer: {
+            Text("Choose a color scheme for the app.")
+        }
+    }
+
     // MARK: - Sports Section
 
     private var sportsSection: some View {