feat(captura): fold recibo OCR into Captura as an automatic mode

Scanning a stack of bills and keying them in are the same daily job, ending
in the same ledger path, so OCR intake becomes a mode of the capture screen
instead of a second menu entry:

- components/Captura.tsx holds the mode switch; the manual check form moves
  verbatim to components/ManualCheckCapture.tsx and the OCR intake to
  components/StatementIntake.tsx.
- /estado-cuenta/lote opens on manual, /recibos on automatic — both render
  Captura, so batch-review links and old bookmarks still land right.
- Nav drops "Recibos (OCR)"; "Captura" covers both, with a NavLink.aliases
  field so /recibos still highlights it.

Also fixes the "El almacenamiento de documentos no está configurado" failure
staff hit on upload. Uploading with no object storage configured used to
succeed, then die on the first put minutes later, leaving a FAILED batch
whose only explanation was that string. createBatch now refuses up front,
GET /statements/status reports storageAvailable alongside ocrAvailable, and
the intake tab explains the situation instead of offering an upload that
cannot work. S3_* documented in .env.example (deploy stacks already set it).

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

apps/api/src/statements/statements.service.ts

@@ -53,6 +53,11 @@ export class StatementsService {
     return this.ocr.available();
   }
 
+  /** Scans are stored as blobs, so no object storage means no intake. */
+  storageAvailable(): boolean {
+    return this.storage.available;
+  }
+
   // --- ingest ---------------------------------------------------------------
 
   /**
@@ -75,6 +80,14 @@ export class StatementsService {
         "El servidor no tiene OCR instalado; no se pueden procesar recibos.",
       );
     }
+    // Checked here rather than at the first `put`, which would only surface as
+    // a FAILED batch minutes later.
+    if (!this.storage.available) {
+      throw new BadRequestException(
+        "El almacenamiento de documentos no está configurado; no se pueden " +
+          "guardar los recibos escaneados.",
+      );
+    }
 
     const batch = await this.prisma.statementBatch.create({
       data: { serviceKind, uploadedById, label, fileCount: files.length },