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/integer_division.h

@@ -0,0 +1,67 @@
+// 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.
+
+#ifndef UTIL_INTEGER_DIVISION_H_
+#define UTIL_INTEGER_DIVISION_H_
+
+#include <type_traits>
+
+namespace openscreen {
+
+// Returns CEIL(num ÷ denom). `denom` must not equal zero. This function is
+// compatible with any integer-like type, including the integer-based
+// std::chrono duration types.
+//
+// Optimization note: See DividePositivesRoundingUp().
+template <typename Integer>
+constexpr auto DivideRoundingUp(Integer num, Integer denom) {
+  if (denom < Integer{0}) {
+    num *= -1;
+    denom *= -1;
+  }
+  if (num < Integer{0}) {
+    return num / denom;
+  }
+  return (num + denom - Integer{1}) / denom;
+}
+
+// Same as DivideRoundingUp(), except is more-efficient for hot code paths that
+// know `num` is always greater or equal to zero, and `denom` is always greater
+// than zero.
+template <typename Integer>
+constexpr Integer DividePositivesRoundingUp(Integer num, Integer denom) {
+  return DivideRoundingUp<typename std::make_unsigned<Integer>::type>(num,
+                                                                      denom);
+}
+
+// Divides `num` by `denom`, and rounds to the nearest integer (exactly halfway
+// between integers will round to the higher integer). This function is
+// compatible with any integer-like type, including the integer-based
+// std::chrono duration types.
+//
+// Optimization note: See DividePositivesRoundingNearest().
+template <typename Integer>
+constexpr auto DivideRoundingNearest(Integer num, Integer denom) {
+  if (denom < Integer{0}) {
+    num *= -1;
+    denom *= -1;
+  }
+  if (num < Integer{0}) {
+    return (num - ((denom - Integer{1}) / 2)) / denom;
+  }
+  return (num + (denom / 2)) / denom;
+}
+
+// Same as DivideRoundingNearest(), except is more-efficient for hot code paths
+// that know `num` is always greater or equal to zero, and `denom` is always
+// greater than zero.
+template <typename Integer>
+constexpr Integer DividePositivesRoundingNearest(Integer num, Integer denom) {
+  return DivideRoundingNearest<typename std::make_unsigned<Integer>::type>(
+      num, denom);
+}
+
+}  // namespace openscreen
+
+#endif  // UTIL_INTEGER_DIVISION_H_