feat(qt): HiFi Wizard — guided DAC setup ported from Slint

Six-step modal (Welcome / Check / DACs / Configure / Test / Done) opened
from Settings > Audio. It probes the audio stack and renders per-distro
remediations, enumerates DACs with a manual node.name escape hatch,
generates the PipeWire / WirePlumber snippets to copy, and plays four
tracks spanning 16/44.1 to 24/192 with a live requested-vs-negotiated
read-back. Read-only: it never writes a system file or runs a command.

The logic was unreachable from Qt — every public function in
qbz-dac-wizard takes a &AppWindow and writes straight into Slint globals.
It is lifted into a new frontend-agnostic crate, qbz-dac-wizard-core,
which returns plain data. qbz-dac-wizard itself is left untouched.

Rust owns everything it computes plus `open`, so the reset and the probe
are one act; QML owns the step navigation and the four progress
checkboxes, which is how the reference splits them too.

Two deliberate divergences from the reference: the row sits at the end of
OUTPUT rather than BIT-PERFECT, and it is offered on every backend
instead of PipeWire only — someone on ALSA direct is exactly who needs
the walkthrough.

The green glyphs use the accent tint, not success: success has no qrc bake
directory, so a degraded tint set would render nothing at all. Every
success-toned text keeps theme.success (#3fae6a verbatim).

Verified by 309 tests, both QML audits and the offscreen smoke, plus a
forced-route probe that mounts Settings and walks the wizard's steps —
the standard smoke only mounts Home, so it is no evidence for a modal.
The modal was also driven and screenshotted over VNC.

cc

crates/qbz-qt/build.rs

@@ -51,7 +51,7 @@ fn main() {
             // (myqbz_qt.rs, blacklist_qt.rs, toast_qt.rs, …) are plain
             // modules and must NOT be listed — only files that declare a
             // #[cxx_qt::bridge] mod belong in this array.
-            rust_files: &["src/bridge.rs", "src/session_bridge.rs", "src/shell_bridge.rs", "src/player_bridge.rs", "src/queue_bridge.rs", "src/home_bridge.rs", "src/viz_bridge.rs", "src/immersive_bridge.rs", "src/suggestions_bridge.rs", "src/hotkeys_bridge.rs", "src/search_bridge.rs", "src/local_bridge.rs", "src/library_bridge.rs", "src/album_bridge.rs", "src/artist_bridge.rs", "src/lyrics_qt.rs", "src/icon_tint_qt.rs", "src/cast_bridge.rs", "src/myqbz_bridge.rs", "src/myqbz_add_bridge.rs", "src/disco_bridge.rs", "src/blacklist_bridge.rs", "src/playlist_picker_bridge.rs", "src/playlist_manager_bridge.rs", "src/playlist_import_bridge.rs", "src/folder_edit_bridge.rs", "src/playlist_edit_bridge.rs", "src/qconnect_bridge.rs", "src/kiosk_nav_bridge.rs", "src/mini_bridge.rs", "src/tray_bridge.rs"],
+            rust_files: &["src/bridge.rs", "src/session_bridge.rs", "src/shell_bridge.rs", "src/player_bridge.rs", "src/queue_bridge.rs", "src/home_bridge.rs", "src/viz_bridge.rs", "src/immersive_bridge.rs", "src/suggestions_bridge.rs", "src/hotkeys_bridge.rs", "src/search_bridge.rs", "src/local_bridge.rs", "src/library_bridge.rs", "src/album_bridge.rs", "src/artist_bridge.rs", "src/lyrics_qt.rs", "src/icon_tint_qt.rs", "src/cast_bridge.rs", "src/myqbz_bridge.rs", "src/myqbz_add_bridge.rs", "src/disco_bridge.rs", "src/blacklist_bridge.rs", "src/playlist_picker_bridge.rs", "src/playlist_manager_bridge.rs", "src/playlist_import_bridge.rs", "src/dac_wizard_bridge.rs", "src/folder_edit_bridge.rs", "src/playlist_edit_bridge.rs", "src/qconnect_bridge.rs", "src/kiosk_nav_bridge.rs", "src/mini_bridge.rs", "src/tray_bridge.rs"],
             qml_files: &[
                 "qml/LoginScreen.qml",
                 "qml/Main.qml",
@@ -67,6 +67,7 @@ fn main() {
                 "qml/cards/TrackCard.qml",
                 "qml/controls/AddToMixtapeModal.qml",
                 "qml/controls/CardMenu.qml",
+                "qml/controls/CommandBlock.qml",
                 "qml/controls/CardOverlayButton.qml",
                 "qml/controls/CardOverlayRow.qml",
                 "qml/controls/FolderEditPanel.qml",
@@ -244,6 +245,7 @@ fn main() {
                 "qml/controls/WarningBanner.qml",
                 "qml/settings/AudioSettings.qml",
                 "qml/settings/BlacklistSettings.qml",
+                "qml/settings/DacWizardModal.qml",
                 "qml/settings/DeveloperSettings.qml",
                 "qml/settings/LibFolderEditModal.qml",
                 "qml/settings/LibraryFolderTable.qml",