Polish: aria-pressed toggles, deferred row styling, override hint

Fund visibility toggles and the header privacy/theme buttons expose
aria-pressed (FE-16); deferred transactions render struck-through and
muted so the state is visible at a glance (UX-05); the balance-override
input documents its keyboard contract (UX-21). The Budget CSV button
rides in the transactions tab header.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

frontend/src/components/transactions/transaction-columns.tsx

@@ -107,6 +107,7 @@ export function getTransactionColumns({
             className={cn(
               'font-mono font-medium',
               tx.transaction_type !== 'COMPRA' && 'text-primary',
+              tx.deferred_to_next_cycle && 'opacity-50 line-through decoration-muted-foreground/60',
             )}
           >
             {tx.transaction_type === 'COMPRA' ? '-' : '+'}