feat: replace mpv with hls.js HTML5 video player (v0.4.0)

- Remove mpvController.ts and hlsTrimmer.ts entirely
  - Rewrite PlaybackService: streamlink --stream-url → HLS-URL → IPC event playback:hls-url
  - Add VideoPlayer.tsx (hls.js <video> wrapper, forwardRef with seek/seekTo/pause/play/stop/getCurrentTime)
  - Integrate VideoPlayer into ChannelScreen with direct videoRef calls (no IPC roundtrip for seek/pause)
  - Add global AppShell playback overlay for direct stream start (A-button in Browse/Category/StreamList)
  - Propagate onStartLive callback through BrowseScreen, CategoryScreen, StreamListScreen
  - Add CORS bypass for Twitch CDN (webRequest.onBeforeSendHeaders) and autoplay-policy switch
  - Update CSP: add media-src 'self' blob: for hls.js MediaSource API
  - Open chapter panel without stopping playback (pause + resume instead of stop/restart)
  - Drop IPC channels: seek, seekTo, resume, togglePause, getCurrentPosition, onTimeUpdate
  - Add IPC channel: playback:hls-url event with HlsUrlPayload

.gitattributes

@@ -0,0 +1,9 @@
+# Alle Textdateien mit LF normalisieren
+* text=auto eol=lf
+
+# Shell-Skripte immer LF
+*.sh text eol=lf
+
+# Windows-spezifische Dateien mit CRLF
+*.bat text eol=crlf
+*.cmd text eol=crlf