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/PlatformMenuPicker.swift

@@ -0,0 +1,42 @@
+//
+//  PlatformMenuPicker.swift
+//  Yattee
+//
+//  A Picker wrapper that renders as a compact menu inside LabeledContent on tvOS,
+//  and as a standard inline Picker on iOS/macOS. Use this for short option lists
+//  in settings forms so tvOS shows a dropdown menu rather than pushing a sub-view.
+//
+
+import SwiftUI
+
+struct PlatformMenuPicker<Selection: Hashable, Label: View, Content: View>: View {
+    @Binding var selection: Selection
+    @ViewBuilder var content: () -> Content
+    @ViewBuilder var label: () -> Label
+
+    var body: some View {
+        #if os(tvOS)
+        LabeledContent {
+            Picker(selection: $selection, content: content) { EmptyView() }
+                .pickerStyle(.menu)
+                .labelsHidden()
+        } label: {
+            label()
+        }
+        #else
+        Picker(selection: $selection, content: content, label: label)
+        #endif
+    }
+}
+
+extension PlatformMenuPicker where Label == Text {
+    init(
+        _ titleKey: String,
+        selection: Binding<Selection>,
+        @ViewBuilder content: @escaping () -> Content
+    ) {
+        self._selection = selection
+        self.content = content
+        self.label = { Text(titleKey) }
+    }
+}