Implement Cast Streaming mirroring, DLNA casting, daemon+GUI, and breadd integration

Builds out the full v1 scope: a vendored+patched openscreen subset for
low-latency Cast Streaming (Mirroring receiver 0F5096E8) alongside the
existing Cast V2/HLS and new DLNA/AVTransport casting paths, breadcastd's
Idle/Casting state machine with a private IPC socket, the breadcast GTK4
popup as a thin IPC client, and bread.cast.*/bread.command.cast.* breadd
integration (device discovery, start/stop, mirroring lifecycle events).
Also adds bakery/systemd/Forgejo CI packaging.

Validated end-to-end against a real Chromecast/Google TV: negotiated
Cast Streaming session, live pipeline playback, and daemon+GUI click-to-cast/
stop through the actual popup.

breadcast-caststream-sys/vendor/openscreen/cast/streaming/capture_configs.h

@@ -0,0 +1,81 @@
+// Copyright 2020 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CAST_STREAMING_CAPTURE_CONFIGS_H_
+#define CAST_STREAMING_CAPTURE_CONFIGS_H_
+
+#include <string>
+#include <vector>
+
+#include "cast/streaming/public/constants.h"
+#include "cast/streaming/resolution.h"
+#include "util/simple_fraction.h"
+
+namespace openscreen::cast {
+
+// A configuration set that can be used by the sender to capture audio, and the
+// receiver to playback audio. Used by Cast Streaming to provide an offer to the
+// receiver.
+struct AudioCaptureConfig {
+  // Audio codec represented by this configuration.
+  AudioCodec codec = AudioCodec::kOpus;
+
+  // Number of channels used by this configuration.
+  int channels = kDefaultAudioChannels;
+
+  // Average bit rate in bits per second used by this configuration. A value
+  // of "zero" suggests that the bitrate should be automatically selected by
+  // the sender.
+  int bit_rate = 0;
+
+  // Sample rate for audio RTP timebase.
+  int sample_rate = kDefaultAudioSampleRate;
+
+  // Target playout delay in milliseconds.
+  std::chrono::milliseconds target_playout_delay = kDefaultTargetPlayoutDelay;
+
+  // The codec parameter for this configuration. Honors the format laid out
+  // in RFC 6381: https://datatracker.ietf.org/doc/html/rfc6381
+  // NOTE: the "profiles" parameter is not supported in our implementation.
+  std::string codec_parameter;
+};
+
+// A configuration set that can be used by the sender to capture video, as
+// well as the receiver to playback video. Used by Cast Streaming to provide an
+// offer to the receiver.
+struct VideoCaptureConfig {
+  // Video codec represented by this configuration.
+  VideoCodec codec = VideoCodec::kVp8;
+
+  // Maximum frame rate in frames per second.
+  // For simple cases, the frame rate may be provided by simply setting the
+  // number to the desired value, e.g. 30 or 60FPS. Some common frame rates like
+  // 23.98 FPS (for NTSC compatibility) are represented as fractions, in this
+  // case 24000/1001.
+  SimpleFraction max_frame_rate{kDefaultFrameRate, 1};
+
+  // Number specifying the maximum bit rate for this stream. A value of
+  // zero means that the maximum bit rate should be automatically selected by
+  // the sender.
+  int max_bit_rate = 0;
+
+  // Resolutions to be offered to the receiver. At least one resolution
+  // must be provided.
+  std::vector<Resolution> resolutions;
+
+  // Target playout delay in milliseconds.
+  std::chrono::milliseconds target_playout_delay = kDefaultTargetPlayoutDelay;
+
+  // The codec parameter for this configuration. Honors the format laid out
+  // in RFC 6381: https://datatracker.ietf.org/doc/html/rfc6381.
+  // VP8 and VP9 codec parameter versions are defined here:
+  // https://developer.mozilla.org/en-US/docs/Web/Media/Formats/codecs_parameter#webm
+  // https://www.webmproject.org/vp9/mp4/#codecs-parameter-string
+  // NOTE: the "profiles" parameter is not supported in our implementation.
+  std::string codec_parameter;
+};
+
+}  // namespace openscreen::cast
+
+#endif  // CAST_STREAMING_CAPTURE_CONFIGS_H_