Add unified page-based details panel on existing layouts

Phase 1 of the player panels redesign:

- New PanelSettings model (pages, regions, layout mode, default
  visibility) stored as an optional field on PlayerControlsLayout with
  an effectivePanelSettings accessor; lenient Codable so future page
  types and settings payloads never corrupt saved presets.
- New Views/Player/Panels content engine: PlayerPanelContentView
  renders a page bar plus the selected page (info, comments, related,
  chapters, queue, tracks), with runtime hiding of empty pages.
- PortraitDetailsPanel and FloatingDetailsPanel now host the shared
  content instead of their duplicated info bodies; drag machinery,
  pills, and fades are untouched.
- Comments list extracted into CommentsListContent shared by the
  overlay and the comments page; comments pill routes to the comments
  page (expanding the portrait panel) when the page is enabled, and
  falls back to the overlay when it is not.
- Tracks page embeds QualitySelectorView via a new isEmbedded mode.
- Deleted the unused video info bodies in ExpandedPlayerSheet+VideoInfo
  and the dead PlayerInfoTab model.

Yattee/Models/PlayerControls/PlayerControlsLayout.swift

@@ -38,6 +38,9 @@ struct PlayerControlsLayout: Codable, Hashable, Sendable {
     /// field still decode.
     var wideLayoutPanelAlignment: FloatingPanelSide?
 
+    /// Details panel pages configuration. Optional for backward compatibility.
+    var panelSettings: PanelSettings?
+
 
     // MARK: - Initialization
 
@@ -59,7 +62,8 @@ struct PlayerControlsLayout: Codable, Hashable, Sendable {
         progressBarSettings: ProgressBarSettings = .default,
         gesturesSettings: GesturesSettings? = nil,
         playerPillSettings: PlayerPillSettings? = nil,
-        miniPlayerSettings: MiniPlayerSettings? = nil
+        miniPlayerSettings: MiniPlayerSettings? = nil,
+        panelSettings: PanelSettings? = nil
     ) {
         self.topSection = topSection
         self.centerSettings = centerSettings
@@ -69,6 +73,7 @@ struct PlayerControlsLayout: Codable, Hashable, Sendable {
         self.gesturesSettings = gesturesSettings
         self.playerPillSettings = playerPillSettings
         self.miniPlayerSettings = miniPlayerSettings
+        self.panelSettings = panelSettings
     }
 
     // MARK: - Gesture Settings
@@ -92,6 +97,13 @@ struct PlayerControlsLayout: Codable, Hashable, Sendable {
         miniPlayerSettings ?? .default
     }
 
+    // MARK: - Panel Settings
+
+    /// Returns the effective details panel settings, using defaults if not set.
+    var effectivePanelSettings: PanelSettings {
+        panelSettings ?? .default
+    }
+
     // MARK: - Defaults
 
     /// Default layout matching the current hardcoded player controls.