perf(cache): migração para diretiva use cache do Next.js

Todas as queries cacheadas do dashboard migram de `unstable_cache` para
a diretiva `use cache` com `cacheTag` e `cacheLife({ revalidate: 3 })`.

Todas as páginas e o layout do dashboard passam a chamar `connection()`
para garantir renderização dinâmica. O root layout envolve os filhos em
`<Suspense>`. `next.config.ts` remove `turbopackFileSystemCacheForDev`
e adota `cacheComponents: true`.

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

src/features/dashboard/preferences-queries.ts

@@ -1,4 +1,5 @@
 import { eq } from "drizzle-orm";
+import { cacheLife, cacheTag } from "next/cache";
 import type { WidgetPreferences } from "@/features/dashboard/widgets/actions";
 import { db, schema } from "@/shared/lib/db";
 
@@ -9,6 +10,10 @@ export interface UserDashboardPreferences {
 export async function fetchUserDashboardPreferences(
 	userId: string,
 ): Promise<UserDashboardPreferences> {
+	"use cache";
+	cacheTag(`dashboard-${userId}`);
+	cacheLife({ revalidate: 3 });
+
 	const result = await db
 		.select({
 			dashboardWidgets: schema.userPreferences.dashboardWidgets,