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/app/globals.css

@@ -1,6 +1,54 @@
 @import "tailwindcss";
 
-@theme inline {
+/*
+ * Ink & copper ledger theme.
+ *
+ * The whole app is written against Tailwind's zinc (neutrals) and indigo
+ * (accent) scales, so the retheme happens here: zinc is remapped to warm
+ * ink/paper tones and indigo to copper. Pages therefore inherit the palette
+ * without per-page edits; chart hexes live in src/lib/category-colors.ts.
+ */
+@theme {
   --font-sans: var(--font-geist-sans);
   --font-mono: var(--font-geist-mono);
+  --font-display: var(--font-fraunces), Georgia, serif;
+
+  /* Ink / paper neutrals (replaces zinc) */
+  --color-zinc-950: #0f0d0a;
+  --color-zinc-900: #171410;
+  --color-zinc-800: #242019;
+  --color-zinc-700: #332d23;
+  --color-zinc-600: #4d4536;
+  --color-zinc-500: #6e644f;
+  --color-zinc-400: #94896f;
+  --color-zinc-300: #b3a88e;
+  --color-zinc-200: #d1c7af;
+  --color-zinc-100: #e8e0cc;
+  --color-zinc-50: #f3edde;
+
+  /* Copper accent (replaces indigo) */
+  --color-indigo-950: #2a1708;
+  --color-indigo-900: #3e2410;
+  --color-indigo-800: #5c3517;
+  --color-indigo-700: #7c4820;
+  --color-indigo-600: #9c5b28;
+  --color-indigo-500: #bc6f30;
+  --color-indigo-400: #d28a47;
+  --color-indigo-300: #e3a968;
+  --color-indigo-200: #efc795;
+  --color-indigo-100: #f7e2c4;
+}
+
+::selection {
+  background: #bc6f30;
+  color: #0f0d0a;
+}
+
+@media (prefers-reduced-motion: reduce) {
+  *,
+  *::before,
+  *::after {
+    animation-duration: 0.01ms !important;
+    transition-duration: 0.01ms !important;
+  }
 }