refactor(slint): extract DAC wizard into qbz-dac-wizard crate

First per-feature crate split off the qbz binary. `dac_wizard.rs` (794 LOC)
was the cleanest candidate: zero cross-feature module deps — it only used
qbz-ui generated types (AppWindow, DacWizardState, …), qbz-audio, qbz-models
and qbz-i18n. Moved verbatim into `qbz-dac-wizard/src/lib.rs` (import
`crate::` -> `qbz_ui::`); the bin now `use qbz_dac_wizard as dac_wizard;` so
its ~20 call sites in main.rs are unchanged. `cargo check -p qbz` green.

cc

crates/Cargo.toml

@@ -23,6 +23,7 @@ members = [
     "qconnect-transport-ws",
     "qconnect-app",
     "qbz-ui",
+    "qbz-dac-wizard",
     "qbz",
     "qbz-credentials",
     "qbz-media-controls",