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/util/alarm.cc

@@ -0,0 +1,131 @@
+// 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 "util/alarm.h"
+
+#include <algorithm>
+
+#include "util/osp_logging.h"
+
+namespace openscreen {
+
+class Alarm::CancelableFunctor {
+ public:
+  explicit CancelableFunctor(Alarm* alarm) : alarm_(alarm) {
+    OSP_CHECK(alarm_);
+    OSP_CHECK(!alarm_->queued_fire_);
+    alarm_->queued_fire_ = this;
+  }
+
+  ~CancelableFunctor() { Cancel(); }
+
+  CancelableFunctor(CancelableFunctor&& other) : alarm_(other.alarm_) {
+    other.alarm_ = nullptr;
+    if (alarm_) {
+      OSP_CHECK_EQ(alarm_->queued_fire_, &other);
+      alarm_->queued_fire_ = this;
+    }
+  }
+
+  CancelableFunctor& operator=(CancelableFunctor&& other) {
+    Cancel();
+    alarm_ = other.alarm_;
+    other.alarm_ = nullptr;
+    if (alarm_) {
+      OSP_CHECK_EQ(alarm_->queued_fire_, &other);
+      alarm_->queued_fire_ = this;
+    }
+    return *this;
+  }
+
+  void operator()() noexcept {
+    if (alarm_) {
+      Alarm* alarm = alarm_;
+      OSP_CHECK_EQ(alarm->queued_fire_, this);
+      alarm->queued_fire_ = nullptr;
+      alarm_ = nullptr;
+      alarm->TryInvoke();
+    }
+  }
+
+  void Cancel() {
+    if (alarm_) {
+      OSP_CHECK_EQ(alarm_->queued_fire_, this);
+      alarm_->queued_fire_ = nullptr;
+      alarm_ = nullptr;
+    }
+  }
+
+ private:
+  raw_ptr<Alarm> alarm_;
+};
+
+Alarm::Alarm(ClockNowFunctionPtr now_function, TaskRunner& task_runner)
+    : now_function_(now_function), task_runner_(task_runner) {
+  OSP_CHECK(now_function_);
+}
+
+Alarm::~Alarm() {
+  if (queued_fire_) {
+    queued_fire_->Cancel();
+    OSP_CHECK(!queued_fire_);
+  }
+}
+
+void Alarm::Cancel() {
+  scheduled_task_ = TaskRunner::Task();
+}
+
+void Alarm::ScheduleWithTask(TaskRunner::Task task,
+                             Clock::time_point desired_alarm_time) {
+  OSP_CHECK(task.valid());
+
+  scheduled_task_ = std::move(task);
+
+  const Clock::time_point now = now_function_();
+  alarm_time_ = std::max(now, desired_alarm_time);
+
+  // Ensure that a later firing will occur, and not too late.
+  if (queued_fire_) {
+    if (next_fire_time_ <= alarm_time_) {
+      return;
+    }
+    queued_fire_->Cancel();
+    OSP_CHECK(!queued_fire_);
+  }
+  InvokeLater(now, alarm_time_);
+}
+
+void Alarm::InvokeLater(Clock::time_point now, Clock::time_point fire_time) {
+  OSP_CHECK(!queued_fire_);
+  next_fire_time_ = fire_time;
+  // Note: Instantiating the CancelableFunctor below sets |this->queued_fire_|.
+  task_runner_->PostTaskWithDelay(CancelableFunctor(this), fire_time - now);
+}
+
+void Alarm::TryInvoke() {
+  if (!scheduled_task_.valid()) {
+    return;  // This Alarm was canceled in the meantime.
+  }
+
+  // If this is an early firing, re-schedule for later. This happens if
+  // Schedule() was called again before this firing had occurred.
+  const Clock::time_point now = now_function_();
+  if (now < alarm_time_) {
+    InvokeLater(now, alarm_time_);
+    return;
+  }
+
+  // Move the client Task to the stack before executing, just in case the task
+  // itself: a) calls any Alarm methods re-entrantly, or b) causes the
+  // destruction of this Alarm instance.
+  // WARNING: `this` is not valid after here!
+  TaskRunner::Task task = std::move(scheduled_task_);
+  task();
+}
+
+// static
+constexpr Clock::time_point Alarm::kImmediately;
+
+}  // namespace openscreen