Complete the tag editor with remote metadata auto-fill.
- qbz-integrations: add frontend-agnostic `discogs` (client + DTOs, Tauri-free)
and `remote_metadata` (unified DTOs + the pure MusicBrainz/Discogs ->
RemoteAlbum* converters). Copied from src-tauri so the Slint frontend can do
remote lookup without depending on the Tauri binary; src-tauri is left fully
untouched (the production build keeps its own copy — no Tauri-build risk).
- tag_editor.rs: search_remote (provider QbzSelect; MusicBrainzClient::new
search_releases_extended / DiscogsClient search_releases, generation-guarded),
select_result, apply_remote (get_release_with_tracks / get_release_metadata ->
full metadata; overwrites album fields + positional per-track title merge;
track-count-mismatch + rate-limit toasts), open_in_browser.
- TagEditorModal: a remote-lookup box (provider + Search, a horizontal result
card strip with select highlight, Apply + open-in-browser). ADR-008: square
badges, no pills.
- state.slint: RemoteResultItem struct + remote fields/actions on TagEditor*.
LocalLibrary Slint port is now feature-complete (scan/folders, artists images,
tag editor manual+remote, tracks bulk). BUILT BLIND — runtime smoke-test pending.
cc