fix(qt): convert the Slint colour literals that made scrims and shadows invisible

Slint writes #RRGGBBAA, Qt parses #AARRGGBB, so a literal copied verbatim does
not come out the wrong colour — it comes out transparent, because the alpha byte
is whatever the red byte used to be.

Seven sites across five modals. Every faked 32px drop shadow in the port was
#00000080 (alpha 00), and the scrims of LogViewerModal and LibFolderEditModal
were #000000bf, so those two modals had been opening with no dark backdrop at
all. The rest of the tree already spells the same scrim #bf000000.

Found by grepping for 8-digit literals of the shape #00xxxxxx. The gradient
stops in MixArtwork and LocalAlbumView that are legitimately transparent, and
the comments in the scene components that warn about this exact trap, were
checked and left alone.

cc

crates/qbz-qt/qml/controls/QbzConfirmModal.qml

@@ -139,7 +139,7 @@ Item {
         width: panel.width
         height: panel.height
         radius: theme.radiusMd
-        color: "#00000080"
+        color: "#80000000"
         opacity: 0.5
     }
 

crates/qbz-qt/qml/settings/LibFolderEditModal.qml

@@ -92,7 +92,7 @@ Item {
     // Scrim — click dismisses.
     Rectangle {
         anchors.fill: parent
-        color: "#000000bf"
+        color: "#bf000000"
         MouseArea {
             anchors.fill: parent
             onClicked: root.close()
@@ -106,7 +106,7 @@ Item {
         width: panel.width + 8
         height: panel.height + 8
         radius: theme.radiusMd
-        color: "#00000080"
+        color: "#80000000"
         z: -1
     }
 

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

@@ -141,7 +141,7 @@ Item {
             width: card.width
             height: card.height
             radius: theme.radiusMd
-            color: "#00000080"
+            color: "#80000000"
             opacity: 0.5
         }
 

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

@@ -137,7 +137,7 @@ Item {
             width: card.width
             height: card.height
             radius: theme.radiusMd
-            color: "#00000080"
+            color: "#80000000"
             opacity: 0.5
         }
 

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

@@ -79,7 +79,7 @@ Item {
     // Dimmed backdrop; a click closes.
     Rectangle {
         anchors.fill: parent
-        color: "#000000bf"
+        color: "#bf000000"
         MouseArea {
             anchors.fill: parent
             onClicked: QbzShell.logClose()
@@ -93,7 +93,7 @@ Item {
         width: panel.width + 8
         height: panel.height + 8
         radius: theme.radiusMd
-        color: "#00000080"
+        color: "#80000000"
     }
 
     Rectangle {