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/Stat.qml

@@ -0,0 +1,44 @@
+// A number and its name. The figure is set in the display serif, which is what
+// makes a screen of statistics read like a page rather than a readout.
+import QtQuick
+import QtQuick.Controls
+import QtQuick.Layouts
+
+import ".."
+
+ColumnLayout {
+    property string label: ""
+    property string value: "—"
+    property string caption: ""
+    property color accent: Theme.ink
+    property int size: 30
+
+    spacing: 2
+    Layout.fillWidth: true
+
+    Label {
+        text: label.toUpperCase()
+        color: Theme.muted
+        font.pixelSize: 10
+        font.letterSpacing: 1.2
+        font.weight: Font.DemiBold
+        font.family: Theme.sansFamily
+    }
+    Label {
+        text: value
+        color: accent
+        font.pixelSize: size
+        font.family: Theme.displayFamily
+        font.letterSpacing: -0.5
+    }
+    Label {
+        visible: caption !== ""
+        text: caption
+        color: Theme.faint
+        font.pixelSize: 11
+        font.family: Theme.sansFamily
+        Layout.fillWidth: true
+        elide: Text.ElideRight
+        wrapMode: Text.WordWrap
+    }
+}