refactor: enhance TimerPage layout and functionality; update theme and tokens for improved design consistency

- Refactored TimerPage component to improve layout and user experience.
- Updated theme configuration to utilize design tokens for better maintainability.
- Introduced new tokens for colors and typography to align with design principles.
- Simplified state management and improved timer functionality.
- Enhanced accessibility and responsiveness of UI elements.

desktop/kadence_desktop/qml/components/Snackbar.qml

@@ -1,6 +1,8 @@
-// Transient messages. Material's own popup, anchored to the bottom.
+// Transient messages, bottom centre, on an ink slab.
 import QtQuick
-import QtQuick.Controls.Material
+import QtQuick.Controls
+
+import ".."
 
 Popup {
     id: snackbar
@@ -13,19 +15,23 @@ Popup {
     }
 
     x: Math.round((parent.width - width) / 2)
-    y: parent.height - height - 72
-    width: Math.min(parent.width - 48, Math.max(260, label.implicitWidth + 48))
-    padding: 16
+    y: parent.height - height - 28
+    width: Math.min(parent.width - 48, Math.max(240, label.implicitWidth + 36))
+    padding: 14
     modal: false
     focus: false
     closePolicy: Popup.NoAutoClose
-    Material.elevation: 6
-    Material.roundedScale: Material.SmallScale
 
-    Label {
+    background: Rectangle {
+        color: Theme.ink
+        radius: 10
+    }
+    contentItem: Label {
         id: label
-        anchors.fill: parent
         text: snackbar.message
+        color: Theme.paper
+        font.pixelSize: 13
+        font.family: Theme.sansFamily
         wrapMode: Text.WordWrap
     }