ui-svelte: fix histogram calculation (#695)

- Fix the histogram calculation to use server provided generation
tokens/second.
- Move histogram to Activities page where it can exist with the rest of
the token metrics

Fixes #681

ui-svelte/src/components/TokenHistogram.svelte

@@ -1,23 +1,11 @@
 <script lang="ts">
-  interface HistogramData {
-    bins: number[];
-    min: number;
-    max: number;
-    binSize: number;
-    p99: number;
-    p95: number;
-    p50: number;
-  }
+  import type { HistogramData } from "../lib/types";
 
-  interface Props {
-    data: HistogramData;
-  }
+  let { data }: { data: HistogramData } = $props();
 
-  let { data }: Props = $props();
-
-  const height = 120;
-  const padding = { top: 10, right: 15, bottom: 25, left: 45 };
-  const viewBoxWidth = 600;
+  const height = 55;
+  const padding = { top: 5, right: 45, bottom: 15, left: 45 };
+  const viewBoxWidth = 1200;
   const chartWidth = viewBoxWidth - padding.left - padding.right;
   const chartHeight = height - padding.top - padding.bottom;
 
@@ -121,9 +109,5 @@
       {data.max.toFixed(1)}
     </text>
 
-    <!-- X-axis label -->
-    <text x={padding.left + chartWidth / 2} y={height - 2} font-size="10" fill="currentColor" opacity="0.6" text-anchor="middle">
-      Tokens/Second Distribution
-    </text>
   </svg>
 </div>