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/impl/rtp_defines.cc

@@ -0,0 +1,113 @@
+// Copyright 2019 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "cast/streaming/impl/rtp_defines.h"
+
+#include "util/osp_logging.h"
+
+namespace openscreen::cast {
+
+RtpPayloadType GetPayloadType(AudioCodec codec, bool use_android_rtp_hack) {
+  if (use_android_rtp_hack) {
+    return RtpPayloadType::kAudioHackForAndroidTV;
+  }
+
+  switch (codec) {
+    case AudioCodec::kAac:
+      return RtpPayloadType::kAudioAac;
+    case AudioCodec::kOpus:
+      return RtpPayloadType::kAudioOpus;
+    case AudioCodec::kNotSpecified:
+      return RtpPayloadType::kAudioVarious;
+    default:
+      OSP_NOTREACHED();
+  }
+}
+
+RtpPayloadType GetPayloadType(VideoCodec codec, bool use_android_rtp_hack) {
+  if (use_android_rtp_hack) {
+    return RtpPayloadType::kVideoHackForAndroidTV;
+  }
+  switch (codec) {
+    // VP8 and VP9 share the same payload type.
+    case VideoCodec::kVp9:
+    case VideoCodec::kVp8:
+      return RtpPayloadType::kVideoVp8;
+
+    // H264 and HEVC/H265 share the same payload type.
+    case VideoCodec::kHevc:  // fallthrough
+    case VideoCodec::kH264:
+      return RtpPayloadType::kVideoH264;
+
+    case VideoCodec::kAv1:
+      return RtpPayloadType::kVideoAv1;
+
+    case VideoCodec::kNotSpecified:
+      return RtpPayloadType::kVideoVarious;
+
+    default:
+      OSP_NOTREACHED();
+  }
+}
+
+StreamType ToStreamType(RtpPayloadType type, bool use_android_rtp_hack) {
+  if (use_android_rtp_hack) {
+    if (type == RtpPayloadType::kAudioHackForAndroidTV) {
+      return StreamType::kAudio;
+    }
+    if (type == RtpPayloadType::kVideoHackForAndroidTV) {
+      return StreamType::kVideo;
+    }
+  }
+
+  if (RtpPayloadType::kAudioFirst <= type &&
+      type <= RtpPayloadType::kAudioLast) {
+    return StreamType::kAudio;
+  }
+  if (RtpPayloadType::kVideoFirst <= type &&
+      type <= RtpPayloadType::kVideoLast) {
+    return StreamType::kVideo;
+  }
+  return StreamType::kUnknown;
+}
+
+bool IsRtpPayloadType(uint8_t raw_byte) {
+  switch (static_cast<RtpPayloadType>(raw_byte)) {
+    case RtpPayloadType::kAudioOpus:
+    case RtpPayloadType::kAudioAac:
+    case RtpPayloadType::kAudioPcm16:
+    case RtpPayloadType::kAudioVarious:
+    case RtpPayloadType::kVideoVp8:
+    case RtpPayloadType::kVideoH264:
+    case RtpPayloadType::kVideoVp9:
+    case RtpPayloadType::kVideoAv1:
+    case RtpPayloadType::kVideoVarious:
+    case RtpPayloadType::kAudioHackForAndroidTV:
+      // Note: RtpPayloadType::kVideoHackForAndroidTV has the same value as
+      // kAudioOpus.
+      return true;
+
+    case RtpPayloadType::kNull:
+      break;
+  }
+  return false;
+}
+
+bool IsRtcpPacketType(uint8_t raw_byte) {
+  switch (static_cast<RtcpPacketType>(raw_byte)) {
+    case RtcpPacketType::kSenderReport:
+    case RtcpPacketType::kReceiverReport:
+    case RtcpPacketType::kSourceDescription:
+    case RtcpPacketType::kApplicationDefined:
+    case RtcpPacketType::kPayloadSpecific:
+    case RtcpPacketType::kExtendedReports:
+      return true;
+
+    case RtcpPacketType::kNull:
+      break;
+  }
+  return false;
+}
+
+}  // namespace openscreen::cast