chore: remove qbzd headless daemon and its client integration

qbzd was a premature daemon experiment that never shipped (gated off
behind QBZD_ENABLED, no user access). Its ratatui 0.29 dependency pinned
unicode-width =0.2.0, which conflicts with slint's annotate-snippets in a
shared workspace. Remove it entirely; it will be reimplemented from
scratch later on the clean, UI-agnostic shell.

- Delete crates/qbzd daemon crate + workspace member (drops ratatui,
  crossterm and the other qbzd-only deps from the lock).
- Delete src-tauri qbzd_discovery (mDNS) + its commands/state wiring in
  lib.rs; drop the direct mdns-sd dep (Chromecast keeps its own via
  qbz-cast).
- Delete remoteApi/remoteEvents/playbackTargetStore; neutralize
  commandRouter to local-only dispatch (isRemote/skipIfRemote are now
  always-false no-ops so the ~100 guard call-sites keep compiling).
- Strip qbzd branches from playbackService and the remote banner from
  NowPlayingBar; excise qbzd from CastPicker (Chromecast/DLNA kept).
- Remove qbzd i18n keys (5 locales), README daemon node, gitignore note.

cargo check (crates + src-tauri) and svelte-check all green.

cc

src-tauri/Cargo.toml

@@ -38,7 +38,6 @@ qbz-library = { path = "../crates/qbz-library" }
 qbz-cast = { path = "../crates/qbz-cast" }
 qbz-cmaf = { path = "../crates/qbz-cmaf" }
 qbz-secrets = { path = "../crates/qbz-secrets" }
-mdns-sd = "0.19"
 qconnect-app = { path = "../crates/qconnect-app" }
 qconnect-core = { path = "../crates/qconnect-core" }
 qconnect-transport-ws = { path = "../crates/qconnect-transport-ws" }