feat(qbz-qt): the quality stamp, ported from Slint per bar mode

The port had one hand-made badge taken from the archived Tauri tree. Slint has
three distinct components and each bar mounts a specific one, so the wrong tree
had cost the stamp its LEDs entirely — they exist only in Slint, derived from
the output backend and mode, and no amount of polishing the Svelte port would
have produced them.

QualityBadge becomes Slint's icon-only mark with its hover tooltip, for cards
and rows. QualityBadgeFull is the icon plus stacked tier and detail. AudioStamp
is the inline two-row form that carries the LEDs: backend blue when engaged,
mode green, purple for a cast session, amber with the renderer name for a peer
Qobuz Connect. New and Classic mount the SongCard stamp column, Large and Small
the inline stamp, matching the .slint mount sites.

The downgrade case follows Slint too: row one reports what is actually being
delivered with an amber arrow, and the catalog maximum moves into the tooltip
next to the reason it was limited.

PlayerBar's LEDs stop reading the settings document, which never knew whether a
backend was engaged, and read the now-playing output state instead — where
Slint reads them.

cc

crates/qbz-qt/qml/shell/NowPlayingBarSmall.qml

@@ -17,7 +17,8 @@
 // next · repeat · "+"), and the right cluster keeps PlayerBarSmall's mount
 // order (Connect · Cast · Settings · ViewMode · Lyrics · Volume · Queue).
 // The "+" opens the same "Add to…" flyout as the full bar; the quality stamp
-// is the shared QualityBadge in "compact" mode, not hand-drawn text.
+// is AudioStamp.qml — the inline 2-row stamp (quality line over the backend /
+// mode LEDs) that PlayerBarSmall.slint mounts, shared with the Large bar.
 //
 // Connect / Cast / Settings / ViewMode are still inert visual replicas where
 // no Qt invokable exists (TODO comments at the call sites); Volume, Queue,
@@ -61,20 +62,6 @@ Rectangle {
         }
     }
 
-    // np_quality_label is "24-bit / 96 kHz" (playback_qt::quality_badge);
-    // QualityBadge wants the raw numbers.
-    readonly property int npBitDepth: {
-        var l = QbzPlayer.npQualityLabel
-        var i = l.indexOf("-bit")
-        return i > 0 ? parseInt(l.substring(0, i)) : 0
-    }
-    readonly property real npSampleRate: {
-        var l = QbzPlayer.npQualityLabel
-        var i = l.indexOf("/")
-        var j = l.indexOf("kHz")
-        return (i >= 0 && j > i) ? parseFloat(l.substring(i + 1, j)) : 0
-    }
-
     function fmt(secs) {
         var m = Math.floor(secs / 60)
         var s = Math.floor(secs % 60)
@@ -368,18 +355,17 @@ Rectangle {
                     height: parent.height
                     spacing: 1
 
-                    // AudioStamp — the shared QualityBadge in its narrow-bar
-                    // "compact" mode (icon + "24/96"), same component the full
-                    // bar uses. POC-NOTE: row 2 (backend/mode LEDs) is not
-                    // rendered here — the Small stamp has no room for it.
-                    QualityBadge {
-                        visible: QbzPlayer.npHasTrack && QbzPlayer.npQualityLabel !== ""
+                    // AudioStamp — the inline 2-row stamp (quality line over
+                    // the backend/mode LEDs), FIRST in the right set.
+                    // PlayerBarSmall.slint clamps it at 150px, widening to
+                    // 280px when a QConnect renderer name is shown (it grows
+                    // leftward into the empty space before the centre
+                    // transport; the right zone's clip is the real guard).
+                    AudioStamp {
+                        visible: QbzPlayer.npHasTrack
                         anchors.verticalCenter: parent.verticalCenter
-                        mode: "compact"
-                        tierOverride: QbzPlayer.npQualityTier === "hires" ? "hires"
-                            : (QbzPlayer.npQualityLabel !== "" ? "cd" : "")
-                        bitDepth: root.npBitDepth
-                        samplingRate: root.npSampleRate
+                        maxWidth: (QbzPlayer.npIsRemote && QbzPlayer.npCastTarget !== "")
+                            ? 280 : 150
                     }
 
                     // Separator: AudioStamp | icon cluster (10px toward the