Resolve URL shorteners and prompt for ambiguous description links

Tapping bit.ly/tinyurl/t.co/etc. in a description or comment previously
opened Safari even when the destination was a playable YouTube URL.
Added an opt-in "Resolve Short Links" toggle under YouTube Enhancements
(off by default) that follows the redirect on tap: if the target is a
YouTube/PeerTube/direct-media URL, open it in-app; otherwise prompt the
user before falling back to yt-dlp extraction or the browser.

Also added a confirmation dialog for non-shortener links that only
matched the loose .externalVideo yt-dlp fallback, so arbitrary web
pages in descriptions no longer silently kick off extraction.

Prompts live on NavigationCoordinator and are dual-hosted by YatteeApp
and ExpandedPlayerSheet so they remain visible whether or not the
expanded player is covering the main view.

Yattee/Core/Settings/SettingsKey.swift

@@ -41,6 +41,9 @@ enum SettingsKey: String, CaseIterable {
     case deArrowAPIURL
     case deArrowThumbnailAPIURL
 
+    // Short link resolution
+    case resolveShortLinksEnabled
+
     // Platform-specific
     case macPlayerMode
     case playerSheetAutoResize

Yattee/Core/Settings/SettingsManager+DeArrow.swift

@@ -87,4 +87,21 @@ extension SettingsManager {
             set(newValue, for: .deArrowThumbnailAPIURL)
         }
     }
+
+    // MARK: - Short Link Resolution
+
+    /// When enabled, taps on known URL shorteners (bit.ly, tinyurl, t.co, …) in
+    /// descriptions and comments follow the redirect and, if the destination is a
+    /// supported YouTube/PeerTube URL, open it in-app. Off by default because it
+    /// performs a network request to the shortener host on tap.
+    var resolveShortLinksEnabled: Bool {
+        get {
+            if let cached = _resolveShortLinksEnabled { return cached }
+            return bool(for: .resolveShortLinksEnabled, default: false)
+        }
+        set {
+            _resolveShortLinksEnabled = newValue
+            set(newValue, for: .resolveShortLinksEnabled)
+        }
+    }
 }