feat(qbz-qt): phase 2 — app shell with 1:1 Slint visual parity

HeaderBar (42px, sidebar cycle, back/forward, centered search replica,
offline badge + flyout, app menu), three-state Sidebar (open 240 / mini
64 / closed 0, 160ms animation, nav rows with exact msgids), NowPlaying
bar SMALL (3px three-color seekbar, art+title+time left, transport
center, quality/volume/queue-toggle right, exact empty state), Queue
panel (300px animated column, Queue/History tabs, exact empty states).
Nav history stack + NowPlayingModel with empty-state defaults behind
new bridge properties/invokables (transport log-and-noop until
playback lands). Icons as pre-baked tinted SVG variants (ColorOverlay
is broken on the software path); Inter fonts bundled; full dark theme
tokens ported from the Slint foundation files.

km

crates/qbz-qt/qml/HomeView.qml

@@ -0,0 +1,31 @@
+// Content view stub for the only mounted route ("home" = Discover > Home).
+// Phase 3 fills this with the real Discover view; for now it proves the
+// content frame, theme and i18n wiring.
+
+import QtQuick
+import com.blitzfc.qbz
+
+Rectangle {
+    color: theme.surfaceMain
+
+    QbzTheme { id: theme }
+
+    Column {
+        anchors.left: parent.left
+        anchors.top: parent.top
+        anchors.margins: theme.spacingXl
+        spacing: theme.spacingSm
+
+        Text {
+            text: QbzBridge.tr("Discover") + " / " + QbzBridge.tr("Home")
+            color: theme.textPrimary
+            font.pixelSize: theme.fontSection
+            font.weight: theme.weightSemibold
+        }
+        Text {
+            text: "QBZ Qt POC — phase 3 fills this view"
+            color: theme.textMuted
+            font.pixelSize: theme.fontLegal
+        }
+    }
+}