fix(slint): track drag no longer stays glued after release

The drag-end relied on the row TouchArea's pointer-up, which only arrives
if the row still holds the grab. Inside a ListView (or a Flickable that
stays interactive) the scroll gesture can steal the grab mid-drag, so the
up never reached the row and the ghost stayed glued to the cursor. Add a
`changed pressed` safety net that ends the drag on any release or grab
cancel (both paths guard on ta.dragging, so end() runs once). Also give
LabelPageView's Flickable the interactive: !DragState.active flag the
other track views already have.

cc

crates/qbz-slint/ui/primitives/TrackRow.slint

@@ -105,6 +105,19 @@ export component TrackRow inherits Rectangle {
                 ta.dragging = false;
             }
         }
+        // Safety net: the `up` above only arrives if this TouchArea still holds
+        // the pointer grab. Inside a ListView (or a Flickable that didn't drop
+        // out of `interactive`), the scroll gesture can steal the grab mid-drag,
+        // so the `up` never reaches us and the ghost stays glued to the cursor.
+        // `pressed` flips to false on BOTH a normal release and a grab cancel,
+        // so ending the drag here guarantees it always clears. Both paths guard
+        // on `ta.dragging`, so whichever fires first wins and end() runs once.
+        changed pressed => {
+            if (!self.pressed && ta.dragging) {
+                DragActions.end();
+                ta.dragging = false;
+            }
+        }
         moved => {
             if (ta.pressed && root.draggable) {
                 if (!ta.dragging