feat: redondeo en el pie de los documentos de ventas y compras (visible según OADM.RoundMthd) y endpoint /api/company/settings

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

apps/web/src/app/features/documents/document-model.ts

@@ -35,6 +35,8 @@ export interface DocTotals {
   /** Total antes de impuestos. */
   net: number;
   tax: number;
+  /** Redondeo del documento, si está marcado. */
+  rounding: number;
   total: number;
 }
 
@@ -52,6 +54,7 @@ export function computeTotals(
   rates: ReadonlyMap<string, number>,
   discountPercent: number,
   expenseRows: readonly ExpenseRow[] = [],
+  rounding = 0,
 ): DocTotals {
   const factor = 1 - discountPercent / 100;
   let subtotal = 0;
@@ -74,7 +77,8 @@ export function computeTotals(
     net: round2(net),
     tax: round2(tax),
     expenses: round2(expenses),
-    total: round2(net + tax + expenses),
+    rounding: round2(rounding),
+    total: round2(net + tax + expenses + rounding),
   };
 }