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/platform/base/interface_info.h

@@ -0,0 +1,86 @@
+// 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 PLATFORM_BASE_INTERFACE_INFO_H_
+#define PLATFORM_BASE_INTERFACE_INFO_H_
+
+#include <stdint.h>
+
+#include <string>
+#include <vector>
+
+#include "platform/base/ip_address.h"
+
+namespace openscreen {
+
+// Unique identifier, usually provided by the operating system, for identifying
+// a specific network interface. This value is used with UdpSocket to join
+// multicast groups, or to make multicast broadcasts. An implementation may
+// choose to make these values anything its UdpSocket implementation will
+// recognize.
+using NetworkInterfaceIndex = int64_t;
+enum : NetworkInterfaceIndex { kInvalidNetworkInterfaceIndex = -1 };
+
+struct IPSubnet {
+  IPAddress address;
+
+  // Prefix length of `address`, which is another way of specifying a subnet
+  // mask. For example, 192.168.0.10/24 is a common representation of the
+  // address 192.168.0.10 with a 24-bit prefix (this describes a range of IPv4
+  // addresses from 192.168.0.0 through 192.168.0.255). Likewise, for IPv6
+  // addresses such as 2001:db8::/96, the concept is the same (this specifies
+  // the range of addresses having the same leading 96 bits).
+  uint8_t prefix_length = 0;
+
+  IPSubnet();
+  IPSubnet(IPAddress address, uint8_t prefix);
+  ~IPSubnet();
+};
+
+struct InterfaceInfo {
+  enum class Type : uint32_t { kEthernet = 0, kWifi, kLoopback, kOther };
+
+  // Interface index, typically as specified by the operating system,
+  // identifying this interface on the host machine.
+  NetworkInterfaceIndex index = kInvalidNetworkInterfaceIndex;
+
+  // MAC address of the interface.  Typically 6 or 16 bytes.  Empty if
+  // unavailable.
+  std::vector<uint8_t> hardware_address;
+
+  // Interface name (e.g. eth0) if available.
+  std::string name;
+
+  // Hardware type of the interface.
+  Type type = Type::kOther;
+
+  // All IP addresses associated with the interface.
+  std::vector<IPSubnet> addresses;
+
+  // Returns an IPAddress of the given type associated with this network
+  // interface, or the false IPAddress if the associated address family is not
+  // supported on this interface.
+  IPAddress GetIpAddressV4() const;
+  IPAddress GetIpAddressV6() const;
+
+  // Returns true if `hardware_address` is non-zero.
+  bool HasHardwareAddress() const;
+
+  InterfaceInfo();
+  InterfaceInfo(NetworkInterfaceIndex index,
+                const uint8_t hardware_address[6],
+                std::string name,
+                Type type,
+                std::vector<IPSubnet> addresses);
+  ~InterfaceInfo();
+};
+
+// Human-readable output (e.g., for logging).
+std::ostream& operator<<(std::ostream& out, InterfaceInfo::Type type);
+std::ostream& operator<<(std::ostream& out, const IPSubnet& subnet);
+std::ostream& operator<<(std::ostream& out, const InterfaceInfo& info);
+
+}  // namespace openscreen
+
+#endif  // PLATFORM_BASE_INTERFACE_INFO_H_