feat(orbit): add shared library foundations and gated host tools

Extract the HTTP host and catalog layer into qbz-control, preserve the
existing daemon API, and keep private session credentials out of SSE.

Scope library stores and scan workers to their host. Share bounded source
search and show Local results alongside Qobuz in the Qt search page.

Add the launch-gated Qt Orbit laboratory and persistent remote-context
banner. Let qbzd run --orbit own and administer its file library through
instance-scoped API and CLI operations. Full remote UI control remains
pending.

Validate library/control/daemon suites, Qt search and QML regressions,
two isolated daemon processes, Qt release build and final cargo check.

cx

crates/qbz-qt/src/bridge.rs

@@ -297,6 +297,7 @@ impl qbz_bridge::QbzBridge {
     /// Slint global is not persisted either: Settings always opens on Audio,
     /// the section only has to survive a Loader unmount WITHIN a session.
     pub fn settings_set_section(mut self: Pin<&mut Self>, index: i32) {
+        if index == 11 && !crate::orbit_qt::enabled() { return; }
         self.as_mut().set_settings_section(index);
     }