feat(ocr): discard abandoned capture batches

A bad scan, the wrong PDFs or a duplicate upload used to leave a batch
sitting in READY_FOR_REVIEW forever, because the only exits were confirm
(posts to the books) or rejecting every page one at a time. Add a
DISCARDED terminal status to both OCR domains and a single endpoint per
domain that rejects every page still pending in one shot.

Discarding is refused once anything has landed: statements once a page is
POSTED, policies once a page is APPLIED. Those batches did real work and
have to be settled page by page.

- POST /statements/batches/:id/discard
- POST /policy-ocr/batches/:id/discard
- shared DiscardBatchCard on both review screens, gated the same way

apps/web/src/app/recibos/[id]/page.tsx

@@ -4,8 +4,10 @@ import { useCallback, useEffect, useMemo, useState } from "react";
 import Link from "next/link";
 import { AppShell } from "@/components/AppShell";
 import { CustomerPicker } from "@/components/CustomerPicker";
+import { DiscardBatchCard } from "@/components/DiscardBatchCard";
 import {
   confirmStatementBatch,
+  discardStatementBatch,
   getStatementBatch,
   listStatementDocuments,
   rejectStatementDocument,
@@ -66,6 +68,7 @@ function BatchReview({ id }: { id: string }) {
   const [docs, setDocs] = useState<StatementDocument[]>([]);
   const [error, setError] = useState<string | null>(null);
   const [loading, setLoading] = useState(true);
+  const [discarding, setDiscarding] = useState(false);
 
   const load = useCallback(async () => {
     try {
@@ -108,9 +111,31 @@ function BatchReview({ id }: { id: string }) {
     (d) => d.status === "MATCHED" && d.matchedCustomer,
   ).length;
 
+  async function discard() {
+    setDiscarding(true);
+    setError(null);
+    try {
+      await discardStatementBatch(id);
+      await load();
+    } catch (e) {
+      setError((e as Error)?.message ?? "No se pudo descartar el lote.");
+    } finally {
+      setDiscarding(false);
+    }
+  }
+
   if (loading) return <div className="state-box">Cargando…</div>;
   if (!batch) return <div className="state-box state-error">{error ?? "No encontrado."}</div>;
 
+  const postedCount = batch.byStatus.POSTED ?? 0;
+  // Discarding is only offered while the batch can still be abandoned whole:
+  // nothing posted to the ledger yet, and not already settled.
+  const canDiscard =
+    canReview &&
+    batch.status !== "DISCARDED" &&
+    batch.status !== "COMPLETED" &&
+    postedCount === 0;
+
   return (
     <div className="stack">
       <header className="page-head">
@@ -146,6 +171,15 @@ function BatchReview({ id }: { id: string }) {
         />
       )}
 
+      {canDiscard && (
+        <DiscardBatchCard
+          busy={discarding}
+          onDiscard={discard}
+          pageCount={docs.length}
+          what="recibo"
+        />
+      )}
+
       <section className="stack">
         {sorted.map((doc) => (
           <DocumentRow
@@ -166,6 +200,7 @@ const STATUS_LABEL_BATCH: Record<string, string> = {
   READY_FOR_REVIEW: "Listo para revisar",
   COMPLETED: "Registrado",
   FAILED: "Falló",
+  DISCARDED: "Descartado",
 };
 
 /**