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>

docs/RECEIPT_CAPTURE_SPEC.md

@@ -136,9 +136,19 @@ single-movement form.
 > `OcrProvider` seam with a self-hosted Tesseract implementation, per-provider
 > parsers for CFE / CESPT / Telnor, a scoped matcher, and a review queue that
 > posts through `BillingService.createBatch` with `source: "OCR"`. Web:
-> `/recibos` (upload + batch list) and `/recibos/:id` (review queue with the
-> page image beside the extracted fields). New abilities `statement:ingest` /
-> `statement:review`, both STAFF.
+> the "Captura automática (OCR)" tab of the Captura screen (upload + batch
+> list) and `/recibos/:id` (review queue with the page image beside the
+> extracted fields). New abilities `statement:ingest` / `statement:review`, both
+> STAFF.
+>
+> Auto-capture is a *mode of* §1.2's capture screen, not a separate menu entry:
+> it is the same daily job with a scanner instead of a keyboard, and both modes
+> post through the same ledger path. `/estado-cuenta/lote` opens the manual tab,
+> `/recibos` the automatic one; both render `components/Captura.tsx`.
+>
+> Requires object storage (`S3_ENDPOINT` + credentials): the scans are kept as
+> blobs. `GET /statements/status` reports `ocrAvailable` and `storageAvailable`,
+> and the upload card hides itself unless both hold.
 >
 > **Measured, not assumed.** Ten real scans (46 pages of CFE, CESPT and Telnor
 > bills) drove every decision below. Against them the shipped parser identifies