feat(ui): ink & copper ledger retheme + analytics redesign

App-wide retheme done at the token layer: Tailwind's zinc scale is remapped
to warm ink/paper neutrals and indigo to copper in globals.css, so every
page inherits the palette. Fraunces (serif display) added for page titles
and hero figures; all figures now render in mono with tabular numerals.

Analytics page redesigned around a month spine — twelve clickable columns
scaled to each month's spend that act as hero, context, and period
navigation. Adds a 'What changed' top-movers panel vs the previous month,
replaces the 8-line category trend chart with per-category sparkline small
multiples, heat-tints the six-month ledger table, and restyles the Pareto,
pace chart, and cashflow strip. Kept: Pareto, cumulative-vs-typical pace,
drill-downs, regular/occasional split.

Insights and Merchants restyled to the same kit; chart tokens centralised
in category-colors.ts (CHART). Cleared the pre-existing lint errors in
insights (typed tooltip, removed any-casts).

src/lib/category-colors.ts

@@ -26,9 +26,21 @@ export const CATEGORY_COLORS: Record<string, string> = {
   other: "#71717a",
 };
 
+// Ink & copper chart tokens — keep in sync with the @theme scales in globals.css.
+export const CHART = {
+  accent: "#bc6f30", // copper (indigo-500)
+  accentSoft: "#d28a47", // copper light (indigo-400)
+  positive: "#34d399",
+  negative: "#e35f4b",
+  axis: "#94896f", // muted paper (zinc-400)
+  faint: "#6e644f", // zinc-500
+  grid: "#242019", // zinc-800
+  dim: "#332d23", // zinc-700 — de-emphasised series
+};
+
 export const TOOLTIP_STYLE = {
-  background: "#18181b",
-  border: "1px solid #3f3f46",
+  background: "#171410",
+  border: "1px solid #332d23",
   borderRadius: 8,
   fontSize: 12,
 };