Use menu-style pickers in tvOS settings

Introduce PlatformMenuPicker that wraps short-option pickers in
LabeledContent + .pickerStyle(.menu) on tvOS so they render as a
compact dropdown instead of pushing a full-screen option list. On
iOS/macOS it falls through to a plain Picker, leaving rendering
unchanged.

Applied across Playback, Subtitles, Sidebar, Privacy, and Advanced
settings. Long language lists in PlaybackSettingsView are left as
push-style.

Yattee/Views/Settings/PrivacySettingsView.swift

@@ -54,7 +54,7 @@ struct PrivacySettingsView: View {
                     isOn: Bindable(settingsManager).saveWatchHistory
                 )
 
-                Picker(
+                PlatformMenuPicker(
                     String(localized: "settings.behavior.historyRetention"),
                     selection: Binding(
                         get: { settingsManager.historyRetentionDays },
@@ -104,7 +104,7 @@ struct PrivacySettingsView: View {
                     isOn: Bindable(settingsManager).saveRecentPlaylists
                 )
 
-                Picker(
+                PlatformMenuPicker(
                     String(localized: "settings.behavior.searchHistoryLimit"),
                     selection: Binding(
                         get: { settingsManager.searchHistoryLimit },