Add optional AVPlayer support for non-streamable MP4/AVC1 formats

AVPlayer has a fundamental limitation with MP4/AVC1 progressive downloads where the moov atom position affects playback start time. When moov is at the end of the file, AVPlayer must download the entire file before starting playback. MPV doesn't have this limitation.

This commit adds an advanced setting to optionally enable these formats in AVPlayer with appropriate warnings:

- Added new setting: "Enable non-streamable formats (MP4/AVC1)"
- Default: disabled (formats hidden, MPV handles them)
- When enabled: MP4/AVC1 formats up to 1080p appear in AVPlayer quality selector
- Resolution limit: 1080p maximum (higher resolutions can't be played properly)
- Clear warning about slow loading and 1080p limitation
- Automatic stream refresh when setting is toggled
- Full import/export support for the setting

Model/Import Export Settings/Exporters/AdvancedSettingsGroupExporter.swift

@@ -6,6 +6,7 @@ final class AdvancedSettingsGroupExporter: SettingsGroupExporter {
         [
             "showPlayNowInBackendContextMenu": Defaults[.showPlayNowInBackendContextMenu],
             "videoLoadingRetryCount": Defaults[.videoLoadingRetryCount],
+            "avPlayerAllowsNonStreamableFormats": Defaults[.avPlayerAllowsNonStreamableFormats],
             "showMPVPlaybackStats": Defaults[.showMPVPlaybackStats],
             "mpvEnableLogging": Defaults[.mpvEnableLogging],
             "mpvCacheSecs": Defaults[.mpvCacheSecs],

Model/Import Export Settings/Importers/AdvancedSettingsGroupImporter.swift

@@ -13,6 +13,10 @@ struct AdvancedSettingsGroupImporter {
             Defaults[.videoLoadingRetryCount] = videoLoadingRetryCount
         }
 
+        if let avPlayerAllowsNonStreamableFormats = json["avPlayerAllowsNonStreamableFormats"].bool {
+            Defaults[.avPlayerAllowsNonStreamableFormats] = avPlayerAllowsNonStreamableFormats
+        }
+
         if let showMPVPlaybackStats = json["showMPVPlaybackStats"].bool {
             Defaults[.showMPVPlaybackStats] = showMPVPlaybackStats
         }