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/lib/dashboard/types.ts

@@ -0,0 +1,57 @@
+export interface Service {
+  name: string;
+  state: string;
+  hasWeb: boolean;
+}
+
+export interface Trace {
+  service: string;
+  operation: string;
+  duration: number;
+  spans: number;
+  hasError: boolean;
+}
+
+export interface DashboardData {
+  services: Service[];
+  traces: Trace[];
+  node: {
+    cpu: number | null;
+    ram: number | null;
+    disk: number | null;
+    load1: number | null;
+    load5: number | null;
+    load15: number | null;
+    netIn: number | null;
+    netOut: number | null;
+  };
+  rps: number[];
+  latency: number[];
+  errors: number[];
+  traceVolume: number[];
+  links: { url: string; label: string }[];
+}
+
+export function safeDur(us: number): string {
+  if (us < 1000) return `${us}\u00b5s`;
+  if (us < 1_000_000) return `${(us / 1000).toFixed(1)}ms`;
+  return `${(us / 1_000_000).toFixed(2)}s`;
+}
+
+export function gaugeColor(v: number | null): string {
+  if (v === null) return "#3fb950";
+  if (v > 80) return "#f85149";
+  if (v > 60) return "#d29922";
+  return "#3fb950";
+}
+
+export function serviceIndicator(state: string): string {
+  switch (state) {
+    case "running":
+      return "bg-green-400";
+    case "jaeger":
+      return "bg-blue-400";
+    default:
+      return "bg-red-400";
+  }
+}