Add custom accent color with system color picker

Add a Custom swatch to the appearance settings accent color grid,
backed by a hex value stored in settings (synced via iCloud like the
rest). iOS uses the native ColorPicker wheel; macOS uses a circular
swatch that opens NSColorPanel, since the SwiftUI color well looks out
of place among the circles. All accent consumers now read the resolved
color through SettingsManager.resolvedAccentColor.

The indigo preset is retired from the grid but kept in the enum, so
users who selected it keep their color until they pick another one.

Claude-Session: https://claude.ai/code/session_0154KH8RAVAvm6iVanhmoW8o

Yattee/Core/Settings/SettingsKey.swift

@@ -13,6 +13,7 @@ enum SettingsKey: String, CaseIterable {
     // General
     case theme
     case accentColor
+    case customAccentColor
     case showWatchedCheckmark
 
     // Playback

Yattee/Core/Settings/SettingsManager+General.swift

@@ -6,6 +6,7 @@
 //
 
 import Foundation
+import SwiftUI
 #if os(iOS)
 import UIKit
 #elseif os(macOS)
@@ -37,6 +38,23 @@ extension SettingsManager {
         }
     }
 
+    var customAccentColor: Color {
+        get {
+            let hex = _customAccentColor ?? string(for: .customAccentColor) ?? ""
+            return Color(hex: hex) ?? AccentColor.default.color
+        }
+        set {
+            let hex = newValue.toHexString()
+            _customAccentColor = hex
+            set(hex, for: .customAccentColor)
+        }
+    }
+
+    /// The effective accent color, resolving `.custom` to the user-picked value.
+    var resolvedAccentColor: Color {
+        accentColor == .custom ? customAccentColor : accentColor.color
+    }
+
     // MARK: - App Icon Settings
 
     var appIcon: AppIcon {

Yattee/Core/Settings/SettingsTypes.swift

@@ -35,10 +35,20 @@ enum AccentColor: String, CaseIterable, Codable {
     case blue
     case purple
     case indigo
+    case custom
 
+    /// Fixed swatches shown in the settings grid; `.custom` is rendered
+    /// separately as a color picker, and `.indigo` is retired from the grid
+    /// but still resolves for users who selected it before it was removed.
+    static var presets: [AccentColor] {
+        allCases.filter { $0 != .custom && $0 != .indigo }
+    }
+
+    /// The color for `.custom` lives in settings storage — resolve through
+    /// `SettingsManager.resolvedAccentColor` instead of this property.
     var color: Color {
         switch self {
-        case .default: return .blue  // System default accent color
+        case .default, .custom: return .blue  // System default accent color
         case .red: return .red
         case .pink: return .pink
         case .orange: return .orange

Yattee/Core/SettingsManager.swift

@@ -28,6 +28,7 @@ final class SettingsManager {
     // Theme
     var _theme: AppTheme?
     var _accentColor: AccentColor?
+    var _customAccentColor: String?
     var _showWatchedCheckmark: Bool?
 
     // Playback
@@ -417,6 +418,7 @@ final class SettingsManager {
     func clearCache() {
         _theme = nil
         _accentColor = nil
+        _customAccentColor = nil
         _showWatchedCheckmark = nil
         _preferredQuality = nil
         _cellularQuality = nil