Add Enigma2/OpenWebif M3U support: program mapping and zap-before-streaming

- Parse #EXTVLCOPT:program=N from M3U playlists (both full and streaming
  parsers, per channel, strict mode) and store it on playlist items
- Transcode multi-program MPEG-TS streams by mapping only the selected
  program's first video and audio stream (DVB teletext/subtitles in the
  program otherwise make FFmpeg fail to produce HLS)
- Optional per-source "zap before streaming" with configurable delay:
  POST /api/openwebif/zap takes sourceId + streamId, requires an enabled,
  zap-enabled M3U source containing that channel, derives the receiver
  from the configured source URL (never from the client), validates the
  Enigma2 service reference, uses a timeout without redirects and does
  not echo the receiver response
- Live TV: Stop button, and stop playback when leaving the page
- Tests for ordinary and program-tagged playlists and the zap endpoint

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

server/index.js

@@ -208,6 +208,7 @@ app.use('/api/probe', require('./routes/probe'));
 app.use('/api/subtitle', require('./routes/subtitle'));
 app.use('/api/settings', require('./routes/settings'));
 app.use('/api/history', require('./routes/history'));
+app.use('/api/openwebif', require('./routes/openwebif'));
 
 // SPA fallback - serve index.html for all non-API routes
 app.get('*', (req, res) => {