Port Video Super Resolution (MetalFX) from upstream PR moonlight-stream#704

Adds an optional MetalFX spatial upscaler to the tvOS video pipeline,
ported from upstream PR moonlight-stream#704 with tvOS-specific fixes and hardening.
Off by default; when enabled it decodes on a dedicated queue, converts
YUV->RGB via Core Image, and MetalFX-upscales the stream to the display
size before enqueuing to the display layer. Only engages when the display
is larger than the stream (e.g. 1080p -> 4K); at native 4K it is bypassed.

tvOS integration the PR omitted / got wrong:
- Add the "Video Super Resolution (MetalFX)" toggle to Moonlight TV
  Settings.bundle (key videoSuperResolution, default off). Without this the
  feature was permanently off on Apple TV as shipped.
- Skip the PR's iOS-only SettingsViewController + storyboard changes.

Hardening over the raw PR:
- +[VideoSuperResolution isDeviceSupported] gates the feature on actual
  MetalFX MTLFXSpatialScaler support so unsupported GPUs fall back to the
  normal pipeline instead of dropping every frame (black screen).
- Disable VSR for the session when the display is not larger than the
  stream, or when scaler configuration fails, instead of running a pointless
  second decode/convert or dropping frames.
- Runtime per-frame fallback: after repeated failures, revert to direct
  enqueue and request a fresh IDR (avoids mixing decoded-RGB and mid-GOP
  compressed samples on one layer).
- Wait for GPU completion before handing the upscaled buffer to the display
  layer (runs on the VSR queue, not main, so no input-latency cost) to fix a
  tearing / pixel-buffer-pool recycle race.
- Make the HDR reconfigure path serialize on the VSR queue without a
  queue->main->queue deadlock against stop().

MetalFX auto weak-links (introduced tvOS 16 > deployment target), so no
extra linker flags are needed. Private-API-free; fork/self-signed only is
not a concern here (this is standard framework usage).

Claude-Session: https://claude.ai/code/session_01QiVtyqxowFKZc8gKnNjevy

Author: bartleman

Limelight/Database/TemporarySettings.h

@@ -31,6 +31,7 @@
 @property (nonatomic) BOOL playAudioOnPC;
 @property (nonatomic) BOOL optimizeGames;
 @property (nonatomic) BOOL enableHdr;
+@property (nonatomic) BOOL videoSuperResolution;
 @property (nonatomic) BOOL btMouseSupport;
 @property (nonatomic) BOOL absoluteTouchMode;
 @property (nonatomic) BOOL statsOverlay;

Limelight/Database/TemporarySettings.m

@@ -40,6 +40,7 @@ - (id) initFromSettings:(Settings*)settings {
     self.useFramePacing = [[NSUserDefaults standardUserDefaults] integerForKey:@"useFramePacing"] != 0;
     self.playAudioOnPC = [[NSUserDefaults standardUserDefaults] boolForKey:@"audioOnPC"];
     self.enableHdr = [[NSUserDefaults standardUserDefaults] boolForKey:@"enableHdr"];
+    self.videoSuperResolution = [[NSUserDefaults standardUserDefaults] boolForKey:@"videoSuperResolution"];
     self.optimizeGames = [[NSUserDefaults standardUserDefaults] boolForKey:@"optimizeGames"];
     self.multiController = [[NSUserDefaults standardUserDefaults] boolForKey:@"multipleControllers"];
     self.swapABXYButtons = [[NSUserDefaults standardUserDefaults] boolForKey:@"swapABXYButtons"];
@@ -80,6 +81,7 @@ - (id) initFromSettings:(Settings*)settings {
     self.useFramePacing = settings.useFramePacing;
     self.playAudioOnPC = settings.playAudioOnPC;
     self.enableHdr = settings.enableHdr;
+    self.videoSuperResolution = [[NSUserDefaults standardUserDefaults] boolForKey:@"videoSuperResolution"];
     self.optimizeGames = settings.optimizeGames;
     self.multiController = settings.multiController;
     self.swapABXYButtons = settings.swapABXYButtons;

Limelight/Stream/StreamManager.m

@@ -149,6 +149,7 @@ - (BOOL) resumeApp:(HttpManager*)hMan receiveSessionUrl:(NSString**)sessionUrl {
 
 - (NSString*) getStatsOverlayText {
     video_stats_t stats;
+    BOOL videoSuperResolutionEnabled = [[NSUserDefaults standardUserDefaults] boolForKey:@"videoSuperResolution"];
 
     if (!_connection) {
         return nil;
@@ -179,11 +180,13 @@ - (NSString*) getStatsOverlayText {
     }
 
     float interval = stats.endTime - stats.startTime;
-    return [NSString stringWithFormat:@"Video stream: %dx%d %.2f FPS (Codec: %@)\nFrames dropped by your network connection: %.2f%%\nAverage network latency: %@%@",
+    NSString* videoEnhancementString = videoSuperResolutionEnabled ? @"\nVideo Enhancement: MetalFX" : @"";
+    return [NSString stringWithFormat:@"Video stream: %dx%d %.2f FPS (Codec: %@)%@\nFrames dropped by your network connection: %.2f%%\nAverage network latency: %@%@",
             _config.width,
             _config.height,
             stats.totalFrames / interval,
             [_connection getActiveCodecName],
+            videoEnhancementString,
             stats.networkDroppedFrames / interval,
             latencyString,
             hostProcessingString];