refactor(dashboard): restructure dashboard components and improve data handling

- Moved dashboard components (Donut, Gauge, Sparkline) to their own files for better organization.
- Created a new DashboardHeader component to manage the header state and display service status.
- Introduced a layout component for the dashboard to encapsulate common layout styles.
- Simplified the Dashboard component by utilizing new components and reducing inline logic.
- Added type definitions for dashboard data in a new types.ts file.
- Enhanced the visual representation of data with improved SVG elements and accessibility attributes.
- Removed redundant code and improved overall readability and maintainability.

src/components/dashboard/no-data.tsx

@@ -0,0 +1,22 @@
+export function NoData() {
+  return (
+    <svg
+      width={200}
+      height={100}
+      viewBox="0 0 200 100"
+      role="img"
+      aria-label="No data available"
+    >
+      <text
+        x={100}
+        y={50}
+        textAnchor="middle"
+        fill="#6e7681"
+        fontSize={12}
+        fontFamily="system-ui,sans-serif"
+      >
+        No data
+      </text>
+    </svg>
+  );
+}