fix(qt6): prevent chips overflowing card boundaries

- Level cards: dynamic height from content instead of fixed 196px
- Level cards: clip: true on container
- CCard: add clip: true globally (content respects radius 12 corners)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontends/qt6/FrontPage.qml

@@ -310,8 +310,10 @@ Rectangle {
                         model: levels
                         delegate: Rectangle {
                             Layout.fillWidth: true
-                            Layout.preferredHeight: 196
+                            Layout.minimumHeight: 170
+                            implicitHeight: lvlContent.implicitHeight + 32
                             radius: 16
+                            clip: true
                             color: lvlMA.containsMouse ? surfaceContainerHighest : surfaceContainerHigh
                             border.color: lvlMA.containsMouse ? modelData.accent : outlineVariant
                             border.width: 1
@@ -334,7 +336,10 @@ Rectangle {
                             }
 
                             ColumnLayout {
-                                anchors.fill: parent
+                                id: lvlContent
+                                anchors.left: parent.left
+                                anchors.right: parent.right
+                                anchors.top: parent.top
                                 anchors.margins: 16
                                 spacing: 8
 

qml/components/core/CCard.qml

@@ -37,6 +37,7 @@ Rectangle {
 
     // ── Geometry ────────────────────────────────────────────────────
     radius: 12
+    clip: true
     implicitWidth: 300
     implicitHeight: contentColumn.implicitHeight