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/pages/DashboardPage.tsx

@@ -124,6 +124,12 @@ function DashboardContent({ budgetId }: { budgetId: string }) {
   const currency = budget.currency
   const availableBalance = totalIncome - totalExpenses + budget.carryover_amount
 
+  const carryover = budget.carryover_amount
+  const carryoverSubtitle = carryover !== 0
+    ? t("dashboard.carryoverIncludes", { amount: formatCurrency(Math.abs(carryover), currency) })
+    : undefined
+  const carryoverIsNegative = carryover < 0
+
   return (
     <div className="space-y-6">
       {/* Summary cards */}
@@ -139,6 +145,8 @@ function DashboardContent({ budgetId }: { budgetId: string }) {
         balance={{
           value: formatCurrency(availableBalance, currency),
           isPositive: availableBalance >= 0,
+          carryoverSubtitle,
+          carryoverIsNegative,
         }}
         t={t}
       />