style(ui): polimento visual — tema, cards, dark mode e landing page

Raio de borda global 0.625rem → 0.7rem; ajustes finos em --card e --border.
DotPattern removido do layout, tela de auth e landing page.
Account-card redesenhado (cores de saldo, tooltip de flags de exclusão).
Budget-card, card-item, calendário (day-cell, event-modal) com layout revisado.
Auth-card-shell simplificado (sem glassmorphism/blob). Landing page com
mainFeatures + extraFeatures em grid único e dark mode nos botões de CTA.
Imagens de preview da landing atualizadas. CSS --data-7..10 removidas.

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

src/shared/components/ui/calendar.tsx

@@ -90,7 +90,7 @@ function Calendar({
 				table: "w-full border-collapse",
 				weekdays: cn("flex", defaultClassNames.weekdays),
 				weekday: cn(
-					"text-muted-foreground rounded-md flex-1 font-normal text-[0.8rem] select-none",
+					"text-muted-foreground rounded-md flex-1 font-normal text-xs select-none",
 					defaultClassNames.weekday,
 				),
 				week: cn("flex w-full mt-2", defaultClassNames.week),
@@ -99,7 +99,7 @@ function Calendar({
 					defaultClassNames.week_number_header,
 				),
 				week_number: cn(
-					"text-[0.8rem] select-none text-muted-foreground",
+					"text-xs select-none text-muted-foreground",
 					defaultClassNames.week_number,
 				),
 				day: cn(