feat(dashboard): add background graphs to cards and improve layout

- Add BgGraph component for subtle background SVG graphs
- Add gradient fills to MiniGraph components
- Track process count over time
- Calculate total API quota usage
- Improve card styling with overlay content

💘 Generated with Crush

Assisted-by: MiniMax-M2.7 via Crush <crush@charm.land>

web/src/styles/global.css

@@ -541,11 +541,22 @@ input::placeholder { color: var(--text-disabled); }
   overflow: hidden;
 }
 .dash-card {
+  position: relative;
   background: var(--bg-card); border: 1px solid var(--border);
   border-radius: var(--radius-lg); padding: 14px 16px;
   display: flex; flex-direction: column; gap: 8px;
   overflow: hidden;
 }
+.dash-card-graph { padding: 0; }
+.dash-bg-graph {
+  position: absolute; inset: 0; width: 100%; height: 100%;
+  opacity: 0.35; pointer-events: none;
+}
+.dash-card-content {
+  position: relative; z-index: 1;
+  padding: 14px 16px;
+  display: flex; flex-direction: column; gap: 8px;
+}
 .dash-span-2 { grid-column: span 2; }
 .dash-card-head {
   display: flex; align-items: center; justify-content: space-between;