Add ffmpeg for HLS stream download support

- Add ffmpeg to Dockerfile.app for container HLS support
- Configure yt-dlp with --downloader ffmpeg --hls-use-mpegts
- Add startup health check warns if ffmpeg missing
- Update DEVELOPMENT.md with ffmpeg prerequisites and troubleshooting
- Add tests for ffmpeg HLS options and health check

tests/unit/test_enhanced_provider.py

@@ -917,4 +917,47 @@ class TestAniworldLoaderCompat:
         """AniworldLoader should extend EnhancedAniWorldLoader."""
         from src.core.providers.enhanced_provider import AniworldLoader
 
-        assert issubclass(AniworldLoader, EnhancedAniWorldLoader)
+        assert issubclass(AniworldLoader, EnhancedAniWorldLoader)
+
+class TestFfmpegHlsOptions:
+    """Test that yt-dlp is configured with ffmpeg for HLS streams."""
+
+    def test_ytdl_opts_include_ffmpeg_for_hls(self, enhanced_loader, tmp_path):
+        """yt-dlp options should include ffmpeg downloader and hls-use-mpegts."""
+        temp_path = str(tmp_path / "temp.mp4")
+        output_path = str(tmp_path / "output.mp4")
+
+        captured_opts = {}
+
+        def capture_ytdl_download(ydl_opts, link):
+            captured_opts.update(ydl_opts)
+            with open(temp_path, "wb") as f:
+                f.write(b"fake-video-data")
+            return True
+
+        with patch(
+            "src.core.providers.enhanced_provider.recovery_strategies"
+        ) as mock_rs, patch(
+            "src.core.providers.enhanced_provider.file_corruption_detector"
+        ) as mock_fcd, patch(
+            "src.core.providers.enhanced_provider.get_integrity_manager"
+        ) as mock_im:
+            mock_rs.handle_network_failure.return_value = (
+                "https://direct.example.com/v.mp4",
+                [],
+            )
+            mock_rs.handle_download_failure.side_effect = capture_ytdl_download
+            mock_fcd.is_valid_video_file.return_value = True
+            mock_im.return_value.store_checksum.return_value = "abc123"
+
+            enhanced_loader._download_with_recovery(
+                1, 1, "test", "German Dub",
+                temp_path, output_path, None,
+            )
+
+        assert captured_opts.get("downloader") == "ffmpeg", (
+            f"Expected downloader='ffmpeg', got {captured_opts.get('downloader')}"
+        )
+        assert captured_opts.get("hls_use_mpegts") is True, (
+            f"Expected hls_use_mpegts=True, got {captured_opts.get('hls_use_mpegts')}"
+        )