style(frontend): prettier charts, drop redundant frame, format net rates

- Sparkline: multi-stop gradient fill, soft drop-shadow under the line,
  dashed grid, glowing pulse on the latest-point marker, pill-shaped
  tooltip with dashed crosshair
- XrayMetricsModal: glow + pulse on the observatory alive dot,
  monospace stamps/listen text
- SystemHistoryModal: keep just the modal's frame around the chart (the
  inner wrapper I'd added stacked a second border on top); strip the
  decimal from Net Up/Down (25.63 KB/s → 25 KB/s) only on this chart's
  formatter

frontend/src/components/Sparkline.css

@@ -5,16 +5,30 @@
 
 .sparkline-svg .cpu-grid-y-text,
 .sparkline-svg .cpu-grid-x-text {
-  fill: rgba(0, 0, 0, 0.65);
+  fill: rgba(0, 0, 0, 0.55);
+  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
+  letter-spacing: 0.2px;
 }
 
 .sparkline-svg .cpu-grid-text {
   fill: rgba(0, 0, 0, 0.88);
 }
 
+.sparkline-svg .cpu-grid-line {
+  stroke: rgba(0, 0, 0, 0.08);
+}
+
+.sparkline-svg .cpu-tooltip-text {
+  pointer-events: none;
+}
+
+.sparkline-svg .cpu-tooltip-pill {
+  filter: drop-shadow(0 2px 6px rgba(0, 0, 0, 0.18));
+}
+
 body.dark .sparkline-svg .cpu-grid-y-text,
 body.dark .sparkline-svg .cpu-grid-x-text {
-  fill: rgba(255, 255, 255, 0.85);
+  fill: rgba(255, 255, 255, 0.7);
 }
 
 body.dark .sparkline-svg .cpu-grid-text {
@@ -22,9 +36,9 @@ body.dark .sparkline-svg .cpu-grid-text {
 }
 
 body.dark .sparkline-svg .cpu-grid-line {
-  stroke: rgba(255, 255, 255, 0.12);
+  stroke: rgba(255, 255, 255, 0.10);
 }
 
-body.dark .sparkline-svg .cpu-grid-h-line {
-  stroke: rgba(255, 255, 255, 0.35);
+body.dark .sparkline-svg .cpu-tooltip-pill {
+  filter: drop-shadow(0 2px 8px rgba(0, 0, 0, 0.6));
 }

frontend/src/components/Sparkline.tsx

@@ -38,10 +38,10 @@ export default function Sparkline({
   strokeWidth = 2,
   maxPoints = 120,
   showGrid = true,
-  gridColor = 'rgba(0,0,0,0.1)',
-  fillOpacity = 0.15,
+  gridColor = 'rgba(0,0,0,0.08)',
+  fillOpacity = 0.22,
   showMarker = true,
-  markerRadius = 2.8,
+  markerRadius = 3,
   showAxes = false,
   yTickStep = 25,
   tickCountX = 4,
@@ -60,7 +60,10 @@ export default function Sparkline({
   const [hoverIdx, setHoverIdx] = useState(-1);
 
   const reactId = useId();
-  const gradId = `spkGrad-${reactId.replace(/[^a-zA-Z0-9]/g, '')}`;
+  const safeId = reactId.replace(/[^a-zA-Z0-9]/g, '');
+  const gradId = `spkGrad-${safeId}`;
+  const shadowId = `spkShadow-${safeId}`;
+  const glowId = `spkGlow-${safeId}`;
 
   useEffect(() => {
     const el = svgRef.current;
@@ -211,6 +214,15 @@ export default function Sparkline({
     return `${val}${lab ? ' • ' + lab : ''}`;
   }, [hoverIdx, dataSlice, labelsSlice, tooltipFormatter, yFormatter]);
 
+  const tooltipPillWidth = Math.max(48, hoverText.length * 6.2 + 14);
+  const hoverPoint = hoverIdx >= 0 ? pointsArr[hoverIdx] : null;
+  const tooltipX = hoverPoint
+    ? Math.max(
+        paddingLeft + 2,
+        Math.min(effectiveVbWidth - paddingRight - tooltipPillWidth - 2, hoverPoint[0] - tooltipPillWidth / 2),
+      )
+    : 0;
+
   return (
     <svg
       ref={svgRef}
@@ -224,9 +236,25 @@ export default function Sparkline({
     >
       <defs>
         <linearGradient id={gradId} x1="0" y1="0" x2="0" y2="1">
-          <stop offset="0%" stopColor={stroke} stopOpacity={fillOpacity} />
+          <stop offset="0%" stopColor={stroke} stopOpacity={Math.min(1, fillOpacity * 1.8)} />
+          <stop offset="50%" stopColor={stroke} stopOpacity={fillOpacity * 0.7} />
           <stop offset="100%" stopColor={stroke} stopOpacity={0} />
         </linearGradient>
+        <filter id={shadowId} x="-10%" y="-50%" width="120%" height="200%">
+          <feGaussianBlur in="SourceAlpha" stdDeviation="2.4" />
+          <feOffset dx="0" dy="2" result="offsetBlur" />
+          <feComponentTransfer>
+            <feFuncA type="linear" slope="0.45" />
+          </feComponentTransfer>
+          <feMerge>
+            <feMergeNode />
+            <feMergeNode in="SourceGraphic" />
+          </feMerge>
+        </filter>
+        <radialGradient id={glowId}>
+          <stop offset="0%" stopColor={stroke} stopOpacity="0.55" />
+          <stop offset="100%" stopColor={stroke} stopOpacity="0" />
+        </radialGradient>
       </defs>
 
       {showGrid && (
@@ -240,6 +268,7 @@ export default function Sparkline({
               y2={g.y2}
               stroke={gridColor}
               strokeWidth={1}
+              strokeDasharray="3 5"
               className="cpu-grid-line"
             />
           ))}
@@ -252,10 +281,10 @@ export default function Sparkline({
             <text
               key={`y${i}`}
               className="cpu-grid-y-text"
-              x={Math.max(0, paddingLeft - 4)}
+              x={Math.max(0, paddingLeft - 6)}
               y={tk.y + 4}
               textAnchor="end"
-              fontSize={10}
+              fontSize={10.5}
             >
               {tk.label}
             </text>
@@ -267,7 +296,7 @@ export default function Sparkline({
               x={tk.x}
               y={paddingTop + drawHeight + 14}
               textAnchor="middle"
-              fontSize={10}
+              fontSize={10.5}
             >
               {tk.label}
             </text>
@@ -283,9 +312,16 @@ export default function Sparkline({
         strokeWidth={strokeWidth}
         strokeLinecap="round"
         strokeLinejoin="round"
+        filter={`url(#${shadowId})`}
       />
       {showMarker && lastPoint && (
-        <circle cx={lastPoint[0]} cy={lastPoint[1]} r={markerRadius} fill={stroke} />
+        <>
+          <circle cx={lastPoint[0]} cy={lastPoint[1]} r={markerRadius * 3} fill={`url(#${glowId})`}>
+            <animate attributeName="r" values={`${markerRadius * 2.4};${markerRadius * 3.4};${markerRadius * 2.4}`} dur="2.6s" repeatCount="indefinite" />
+          </circle>
+          <circle cx={lastPoint[0]} cy={lastPoint[1]} r={markerRadius + 1.5} fill={stroke} fillOpacity={0.25} />
+          <circle cx={lastPoint[0]} cy={lastPoint[1]} r={markerRadius} fill={stroke} stroke="#fff" strokeWidth={1.5} />
+        </>
       )}
 
       {showTooltip && hoverIdx >= 0 && pointsArr[hoverIdx] && (
@@ -296,16 +332,32 @@ export default function Sparkline({
             x2={pointsArr[hoverIdx][0]}
             y1={paddingTop}
             y2={paddingTop + drawHeight}
-            stroke="rgba(0,0,0,0.2)"
+            stroke={stroke}
+            strokeOpacity={0.45}
             strokeWidth={1}
+            strokeDasharray="3 4"
+          />
+          <circle cx={pointsArr[hoverIdx][0]} cy={pointsArr[hoverIdx][1]} r={5} fill={stroke} fillOpacity={0.25} />
+          <circle cx={pointsArr[hoverIdx][0]} cy={pointsArr[hoverIdx][1]} r={3.5} fill={stroke} stroke="#fff" strokeWidth={1.5} />
+          <rect
+            x={tooltipX}
+            y={paddingTop + 2}
+            width={tooltipPillWidth}
+            height={18}
+            rx={9}
+            ry={9}
+            className="cpu-tooltip-pill"
+            fill={stroke}
+            fillOpacity={0.92}
           />
-          <circle cx={pointsArr[hoverIdx][0]} cy={pointsArr[hoverIdx][1]} r={3.5} fill={stroke} />
           <text
-            className="cpu-grid-text"
-            x={pointsArr[hoverIdx][0]}
-            y={paddingTop + 12}
+            className="cpu-tooltip-text"
+            x={tooltipX + tooltipPillWidth / 2}
+            y={paddingTop + 14}
             textAnchor="middle"
             fontSize={11}
+            fontWeight={600}
+            fill="#fff"
           >
             {hoverText}
           </text>

frontend/src/pages/index/SystemHistoryModal.css

@@ -8,11 +8,29 @@
 }
 
 .cpu-chart-wrap {
-  padding: 8px 16px 16px;
+  margin: 8px 8px 16px;
+  padding: 16px 18px 18px;
+  border-radius: 14px;
+  background: linear-gradient(180deg, rgba(99, 102, 241, 0.05), rgba(99, 102, 241, 0));
+  border: 1px solid rgba(99, 102, 241, 0.12);
+  box-shadow: 0 2px 12px rgba(99, 102, 241, 0.06);
+}
+
+body.dark .cpu-chart-wrap {
+  background: linear-gradient(180deg, rgba(129, 140, 248, 0.08), rgba(129, 140, 248, 0));
+  border-color: rgba(129, 140, 248, 0.16);
+  box-shadow: 0 2px 16px rgba(0, 0, 0, 0.25);
+}
+
+html[data-theme='ultra-dark'] .cpu-chart-wrap {
+  background: linear-gradient(180deg, rgba(129, 140, 248, 0.05), rgba(129, 140, 248, 0));
+  border-color: rgba(129, 140, 248, 0.10);
 }
 
 .cpu-chart-meta {
-  margin-bottom: 10px;
-  font-size: 11px;
+  margin-bottom: 12px;
+  font-size: 11.5px;
   opacity: 0.65;
+  letter-spacing: 0.3px;
+  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
 }

frontend/src/pages/index/SystemHistoryModal.tsx

@@ -35,7 +35,7 @@ const METRICS: MetricDef[] = [
 
 function unitFormatter(unit: string, activeKey: string): (v: number) => string {
   if (unit === 'B/s') {
-    return (v) => `${SizeFormatter.sizeFormat(Math.max(0, Number(v) || 0))}/s`;
+    return (v) => `${SizeFormatter.sizeFormat(Math.max(0, Number(v) || 0)).replace(/\.\d+/, '')}/s`;
   }
   if (unit === '%') {
     return (v) => `${Number(v).toFixed(1)}%`;

frontend/src/pages/index/XrayMetricsModal.css

@@ -29,6 +29,8 @@
 
 .obs-stamp {
   opacity: 0.7;
+  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
+  font-size: 11.5px;
 }
 
 .obs-dot {
@@ -38,16 +40,30 @@
   border-radius: 50%;
   margin-right: 6px;
   vertical-align: middle;
+  box-shadow: 0 0 0 3px rgba(82, 196, 26, 0.18);
 }
 
 .obs-dot.is-alive {
   background: #52c41a;
+  box-shadow: 0 0 0 3px rgba(82, 196, 26, 0.22);
+  animation: obs-dot-pulse 2.2s ease-in-out infinite;
 }
 
 .obs-dot.is-dead {
   background: #f5222d;
+  box-shadow: 0 0 0 3px rgba(245, 34, 45, 0.22);
+}
+
+@keyframes obs-dot-pulse {
+  0%, 100% { box-shadow: 0 0 0 3px rgba(82, 196, 26, 0.22); }
+  50% { box-shadow: 0 0 0 6px rgba(82, 196, 26, 0.06); }
+}
+
+@media (prefers-reduced-motion: reduce) {
+  .obs-dot.is-alive { animation: none; }
 }
 
 .listen-tag {
   opacity: 0.7;
+  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
 }