Fix theme text visibility, tooltip colours, and chart hover states

- Extract shared TOOLTIP_STYLE and ACTIVE_DOT to utils/chartTheme.ts so
  all four chart files use one source of truth
- itemStyle now uses card-foreground (not muted-foreground) — guarantees
  tooltip text is readable on all themes including Terminal, Vault, Synthwave
- cursor now uses primary at 12% opacity — always visible and thematic,
  replaces near-invisible muted-foreground at 8% opacity
- activeDot is now explicit on every Line/Area — prevents Recharts default
  white dot breaking dark themes
- Terminal: muted-foreground bumped 38%→55% lightness, border lightened,
  warning brightened, text-shadow scoped to headings/labels/table cells
  (was applying to every p and span, causing tooltip glow bleed)
- Synthwave: muted-foreground bumped 56%→68% lightness for legibility
- Vault: muted-foreground bumped 52%→60% lightness

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/utils/chartTheme.ts

@@ -0,0 +1,40 @@
+/**
+ * Shared Recharts tooltip and chart style constants.
+ *
+ * All colour values use CSS custom properties so they adapt to every theme.
+ * itemStyle uses card-foreground (not muted-foreground) to guarantee
+ * readability inside the tooltip card on all themes including Terminal,
+ * Synthwave and Vault which have dim muted-foreground values.
+ *
+ * cursor uses --primary at low opacity — always visible and thematic.
+ */
+export const TOOLTIP_STYLE = {
+  contentStyle: {
+    background: "hsl(var(--card))",
+    border: "1px solid hsl(var(--border))",
+    borderRadius: "8px",
+    fontSize: "12px",
+    color: "hsl(var(--card-foreground))",
+    boxShadow: "0 4px 20px rgba(0,0,0,0.35)",
+    padding: "8px 12px",
+  },
+  labelStyle: {
+    color: "hsl(var(--card-foreground))",
+    fontWeight: 600,
+    marginBottom: "4px",
+    fontSize: "12px",
+  },
+  itemStyle: {
+    color: "hsl(var(--card-foreground))",
+    opacity: 0.8,
+  },
+  cursor: { fill: "hsl(var(--primary))", fillOpacity: 0.12 },
+};
+
+/** Standard activeDot for Line/Area charts — theme-adaptive. */
+export const ACTIVE_DOT = {
+  r: 4,
+  stroke: "hsl(var(--card))",
+  strokeWidth: 2,
+  fill: "hsl(var(--primary))",
+};