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.

vendor/rust_cast-0.21.0/.husky/commit-msg

@@ -0,0 +1 @@
+npx --no -- commitlint --edit ${1}

vendor/rust_cast-0.21.0/.husky/pre-push

@@ -0,0 +1,30 @@
+#!/bin/sh
+
+set -eu
+
+if ! cargo +nightly fmt --all -- --check
+then
+    echo "There are some code style issues."
+    echo "Run `cargo fmt` first."
+    exit 1
+fi
+
+if ! cargo clippy --all-targets -- -D warnings
+then
+    echo "There are some clippy issues."
+    exit 1
+fi
+
+if ! cargo test
+then
+    echo "There are some test issues."
+    exit 1
+fi
+
+if ! cargo test --features thread_safe
+then
+    echo "There are some test issues (with `thread_safe` feature)."
+    exit 1
+fi
+
+exit 0