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/uuid.h

@@ -0,0 +1,81 @@
+// Copyright 2025 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_UUID_H_
+#define UTIL_UUID_H_
+
+#include <stdint.h>
+
+#include <compare>
+#include <iosfwd>
+#include <string>
+#include <string_view>
+
+#include "platform/base/span.h"
+
+namespace openscreen {
+
+// UUID implementation strongly based off of Chromium's base::Uuid
+// implementation. Provides securely generated random Uuids as well as parsing
+// logic for inputted UUIDs.
+class Uuid {
+ public:
+  // Length in bytes of the input required to format the input as a Uuid in the
+  // form of version 4.
+  static constexpr size_t kGuidV4InputLength = 16;
+
+  // Generate a 128-bit random Uuid in the form of version 4. see RFC 4122,
+  // section 4.4. The format of Uuid version 4 must be
+  // xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx, where y is one of [8, 9, a, b]. The
+  // hexadecimal values "a" through "f" are output as lower case characters.
+  static Uuid GenerateRandomV4();
+
+  // Returns a valid Uuid if the input string conforms to the Uuid format, and
+  // an invalid Uuid otherwise. Accepts both lower case and upper case hex
+  // characters.
+  static Uuid ParseCaseInsensitive(std::string_view input);
+
+  // Similar to ParseCaseInsensitive(), but all hexadecimal values "a" through
+  // "f" must be lower case characters.
+  static Uuid ParseLowercase(std::string_view input);
+
+  // Constructs an invalid Uuid.
+  Uuid();
+
+  Uuid(const Uuid& other);
+  Uuid(Uuid&& other) noexcept;
+  Uuid& operator=(const Uuid& other);
+  Uuid& operator=(Uuid&& other);
+
+  bool is_valid() const { return !lowercase_.empty(); }
+
+  // Returns the Uuid in a lowercase string format if it is valid, and an empty
+  // string otherwise. The returned value is guaranteed to be parsed by
+  // ParseLowercase().
+  const std::string& AsLowercaseString() const;
+
+  // Invalid Uuids are equal.
+  friend bool operator==(const Uuid&, const Uuid&) = default;
+  // Uuids are 128bit chunks of data so must be indistinguishable if equivalent.
+  friend std::strong_ordering operator<=>(const Uuid&, const Uuid&) = default;
+
+ private:
+  static Uuid FormatRandomDataAsV4Impl(ByteView input);
+
+  // The lowercase form of the Uuid. Empty for invalid Uuids.
+  std::string lowercase_;
+};
+
+// For runtime usage only. Do not store the result of this hash, as it may
+// change in the future.
+struct UuidHash {
+  size_t operator()(const Uuid& uuid) const;
+};
+
+// Stream operator so Uuid objects can be used in logging statements.
+std::ostream& operator<<(std::ostream& out, const Uuid& uuid);
+
+}  // namespace openscreen
+
+#endif  // UTIL_UUID_H_