feat(03-01): add CSS animation tokens, i18n keys, and carryover display

- Add collapsible-open/close keyframes and CSS animation tokens to index.css
- Add dashboard.sections and dashboard.carryoverIncludes keys to en.json and de.json
- Add optional subtitle/subtitleClassName props to StatCard
- Extend SummaryStrip balance prop with carryoverSubtitle/carryoverIsNegative
- Compute and pass carryover subtitle from DashboardContent to SummaryStrip

src/index.css

@@ -71,9 +71,23 @@
 
   --radius: 0.625rem;
 
+  /* Collapsible animation */
+  --animate-collapsible-open: collapsible-open 200ms ease-out;
+  --animate-collapsible-close: collapsible-close 200ms ease-out;
+
   --font-sans: "Inter", ui-sans-serif, system-ui, sans-serif;
 }
 
+@keyframes collapsible-open {
+  from { height: 0; overflow: hidden; }
+  to   { height: var(--radix-collapsible-content-height); overflow: hidden; }
+}
+
+@keyframes collapsible-close {
+  from { height: var(--radix-collapsible-content-height); overflow: hidden; }
+  to   { height: 0; overflow: hidden; }
+}
+
 @layer base {
   * {
     @apply border-border;