Remove unused Sparkline.tsx (replaced by MiniChart)

Closes #52

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ui/src/components/shared/Sparkline.tsx

@@ -1,61 +0,0 @@
-import { useMemo, useRef } from 'react';
-
-interface SparklineProps {
-  data: number[];
-  color: string;
-}
-
-export function Sparkline({ data, color }: SparklineProps) {
-  const gradientIdRef = useRef('spark-' + Math.random().toString(36).slice(2, 9));
-  const gradientId = gradientIdRef.current;
-
-  // Drop first and last buckets — they are partial time windows and skew the trend
-  const trimmed = useMemo(() => (data.length > 4 ? data.slice(1, -1) : data), [data]);
-
-  const { linePath, fillPath } = useMemo(() => {
-    if (trimmed.length < 2) return { linePath: '', fillPath: '' };
-
-    const w = 200;
-    const h = 24;
-    const max = Math.max(...trimmed);
-    const min = Math.min(...trimmed);
-    const range = max - min || 1;
-    const step = w / (trimmed.length - 1);
-
-    const points = trimmed.map(
-      (v, i) => `${i * step},${h - ((v - min) / range) * (h - 2) - 1}`,
-    );
-
-    return {
-      linePath: points.join(' '),
-      fillPath: `0,${h} ${points.join(' ')} ${w},${h}`,
-    };
-  }, [trimmed]);
-
-  if (trimmed.length < 2) return null;
-
-  return (
-    <div style={{ marginTop: 10, height: 24 }}>
-      <svg
-        viewBox="0 0 200 24"
-        preserveAspectRatio="none"
-        style={{ width: '100%', height: '100%' }}
-      >
-        <defs>
-          <linearGradient id={gradientId} x1="0" y1="0" x2="0" y2="1">
-            <stop offset="0%" stopColor={color} stopOpacity={0.3} />
-            <stop offset="100%" stopColor={color} stopOpacity={0} />
-          </linearGradient>
-        </defs>
-        <polygon points={fillPath} fill={`url(#${gradientId})`} />
-        <polyline
-          points={linePath}
-          fill="none"
-          stroke={color}
-          strokeWidth="1.5"
-          strokeLinejoin="round"
-        />
-      </svg>
-    </div>
-  );
-}