perf: otimizar dashboard com indexes, cache e consolidação de queries (v1.3.0)

- Adicionar indexes compostos em lancamentos para queries frequentes
- Eliminar ~20 JOINs com pagadores via helper cacheado getAdminPagadorId()
- Consolidar queries: income-expense-balance (12→1), payment-status (2→1), categories (4→2)
- Adicionar cache cross-request via unstable_cache com tag-based invalidation
- Limitar scan de métricas a 24 meses
- Deduplicar auth session por request via React.cache()

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

lib/dashboard/fetch-dashboard-data.ts

@@ -1,3 +1,4 @@
+import { unstable_cache } from "next/cache";
 import { fetchDashboardAccounts } from "./accounts";
 import { fetchDashboardBoletos } from "./boletos";
 import { fetchExpensesByCategory } from "./categories/expenses-by-category";
@@ -17,7 +18,7 @@ import { fetchPurchasesByCategory } from "./purchases-by-category";
 import { fetchRecentTransactions } from "./recent-transactions";
 import { fetchTopEstablishments } from "./top-establishments";
 
-export async function fetchDashboardData(userId: string, period: string) {
+async function fetchDashboardDataInternal(userId: string, period: string) {
 	const [
 		metrics,
 		accountsSnapshot,
@@ -83,4 +84,20 @@ export async function fetchDashboardData(userId: string, period: string) {
 	};
 }
 
+/**
+ * Cached dashboard data fetcher.
+ * Uses unstable_cache with tags for revalidation on mutations.
+ * Cache is keyed by userId + period, and invalidated via "dashboard" tag.
+ */
+export function fetchDashboardData(userId: string, period: string) {
+	return unstable_cache(
+		() => fetchDashboardDataInternal(userId, period),
+		[`dashboard-${userId}-${period}`],
+		{
+			tags: ["dashboard", `dashboard-${userId}`],
+			revalidate: 120,
+		},
+	)();
+}
+
 export type DashboardData = Awaited<ReturnType<typeof fetchDashboardData>>;