feat(bank): multi-bank chequera — required bankAccountId, per-account scoping

The office keeps more than one operating account (Utilities banks in MXN,
Seguros in USD), but bank_transactions was a single implicit MXN register by
design. Adds Bank/BankAccount and makes every read and write in the module
scoped to exactly one account.

Schema:
- Bank / BankAccount. Currency is fixed per account and BankTransaction has
  no currency column of its own — a movement inherits its account's, the way
  a real bank account doesn't mix currencies.
- BankTransaction.bankAccountId, required. A movement with no known account
  isn't reconcilable against a statement.
- @@index([bankAccountId, transactionDate]): every read now filters by
  account and orders/groups by date.

Migration:
- backfill_bank_accounts.py seeds Scotiabank + "Utilities — Scotiabank (MXN)"
  and backfills all 22,669 existing rows onto it, then promotes the column to
  NOT NULL and attaches the FK. Standalone because prisma db push cannot add
  a required column to a populated table. Idempotent; re-running once a second
  account exists does not re-point rows.
- run_all.py runs it (both modes) before transform_bank.py, which now resolves
  the account by label and fails fast if it is missing.

API:
- ?bankAccountId= required on list/stats/facets/summary — not optional with an
  "all accounts" default, since summing an MXN and a USD register repeats the
  currency-collapsing mistake the billing module exists to prevent. Missing is
  400, unknown is 404.
- facets() had no account clause at all and summary() has two raw-SQL rollups;
  all three are now parameterised. Scoping only one of summary's queries would
  leave the year list and its drill-down describing different books.
- New bank/accounts + bank/banks sub-resource under a MANAGER
  bank:manage-accounts ability. currency is absent from the update DTO: booked
  movements are denominated in it, so editing would re-denominate history.
  Capture into a closed account is rejected.

Web:
- /banco gains an account picker (remembered per browser) and reads every
  figure in the selected account's currency; the "single currency (MXN)"
  doc-comment and the hardcoded MXN formatting are gone.
- New /banco/cuentas for banks and accounts. Accounts are closed, never
  deleted — the FK is required, so deleting one would destroy its register.
- /inicio's chequera card names the account it is reading instead of implying
  a single register.

Verified against dev + browser: a second USD account showed full read/write
isolation from the MXN register, whose totals were unchanged (22,669
movements, net 1,014,266.97).

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

PLAN.md

@@ -135,7 +135,7 @@ Given the amount of near-duplicate/overlapping data across snapshot tables (mult
       **Two pre-existing bugs found and fixed while building it:** (a) `statement()` filtered `legacySourceTable: { notIn: [...] }`, which compiles to SQL `NOT IN` — and `NULL NOT IN (…)` is NULL, so **every app-captured movement was invisible on the customer statement** (438 rows in the movement browser vs 392 on the statement) while still appearing everywhere else. This would have made the whole receipt-capture feature look broken to staff. Now NULL-safe. (b) The balances *count* query omitted the void filter its own page query applied, so the row count disagreed with the rows.
       **OCR seam:** `BillingService.createBatch(dto, opts)` is the single multi-row write path and carries three contract guarantees for the step-11 OCR module to post through — `items[i]` maps to `lines[i]` (so `StatementDocument.postedTransactionId` can be zipped back on), `opts.refs[i]` stamps `captureRef` with a duplicate-post guard that a *voided* row deliberately does not block, and `opts.source` is service-level only so an HTTP client cannot label hand-keyed rows as machine-captured. Backed by a new `TransactionCaptureSource` enum (MANUAL/BATCH/OCR) + `captureRef`, both nullable so the 40,136 migrated rows stay NULL rather than being mislabelled.
     - **PDF/OCR auto-capture** — ingest→split→OCR→match→review pipeline for the 300+/month/service-provider statements staff currently key in by hand. Posts through the capture module above. Matching logic was checked field-by-field against `migration/transform_properties.py`'s actual output and found three real gaps to close first: no `TELEPHONE` service kind exists yet, `PROPERTY_TAX.accountNumber` was migrated from `PREDIAL` not `CLAVE` (needs verification against a real predial statement), and `GAS.meterNumber` was never populated by the migration at all.
-    - **Multi-bank chequera** — `Bank`/`BankAccount` models so Seguros (US bank) and Utilities (Mexican bank, currently SCOTHIA) can each have their own register; today's `bank_transactions` is hardcoded single-account/MXN-only by design (see step 7 above) and needs a required `bankAccountId` plus scoping added to every read path in `bank.service.ts`, including two raw-SQL queries in `summary()`.
+    - **Multi-bank chequera — DONE** (2026-07-27). `Bank`/`BankAccount` models so Seguros (US bank) and Utilities (Mexican bank, currently SCOTHIA) can each have their own register. `bank_transactions` gained a **required** `bankAccountId` (plus an `(bankAccountId, transactionDate)` index, since every read is now filtered by account and ordered by date), and all 22,669 existing rows were backfilled onto a seeded "Utilities — Scotiabank (MXN)" account by `migration/backfill_bank_accounts.py` — a standalone step because `prisma db push` cannot add a required column to a populated table. It is idempotent and now runs inside `run_all.py` (both normal and `--sync`) ahead of `transform_bank.py`, which fails fast if the account is missing. Every read path in `bank.service.ts` is account-scoped, including `facets()` (which had no filter at all) and *both* raw-SQL rollups in `summary()`. API: `?bankAccountId=` is required on `list`/`stats`/`facets`/`summary` — **not** optional-with-an-all-accounts-default, since summing an MXN and a USD register repeats exactly the currency-collapsing mistake the billing module exists to prevent — plus a new `bank/accounts` + `bank/banks` sub-resource under a MANAGER `bank:manage-accounts` ability. Web: `/banco` gained an account picker (remembered per browser) and reads every figure in the selected account's currency, `/banco/cuentas` manages banks and accounts, and `/inicio`'s chequera card names the account it is showing instead of implying one register. An account's `currency` is immutable after creation by design — its booked movements are denominated in it. Verified against dev + browser: a second USD account showed full read/write isolation from the MXN register, whose totals were unchanged.
     - **Customer-number recycling** — promotes the legacy `NUM id` (currently only inside `customer_legacy_refs`) into a first-class, reusable `Customer.customerNumber`, automates *finding* candidates for reuse (cancelled / 1-year-inactive), and auto-assigns the lowest free number at creation — the search is automated, the release/reuse decision stays a human action. Backfill needs care: ~140 utilities rows and all insurance-only customers have no real legacy number (synthetic `rownum_N`/`insrow_N` placeholders in `transform_customers.py`, not real `NUM id`s).
     
     Several open questions block parts of this (OCR provider/budget, the Seguros bank's identity, the clave-catastral-vs-predial mismatch, exact recycling triggers, and whether "recycling" should ever mean true data purge vs. archive-and-reuse-the-number) — see the spec's collected open-questions section.
@@ -185,7 +185,7 @@ Unlike the ops items above, these block design decisions, not just infrastructur
 
 - OCR provider/budget for the statement auto-capture pipeline (self-hosted vs. a paid per-page API, given 300+ statements/month/service provider).
 - Whether `PROPERTY_TAX.accountNumber` (migrated from `DATMEX.PREDIAL`) is actually the same number as "Clave Catastral" (`DATMEX.CLAVE`) — blocks OCR matching for predial statements until confirmed against a real bill.
-- The actual bank name/currency/details for the Seguros USD account, and whether any historical Seguros bank register exists to migrate.
+- The actual bank name/currency/details for the Seguros USD account, and whether any historical Seguros bank register exists to migrate. (Multi-bank support itself is **built** — this is now only the missing content: staff can open the account in `/banco/cuentas` the moment the answer arrives, and it starts empty unless a historical register turns up.)
 - The exact "1 year inactivity" / "cancelled" triggers for customer-number recycling eligibility.
 - Whether customer-number recycling should ever include true PII purge (matching the office's paper-world habit) or archive-and-reuse-the-number is sufficient — recommended default is archive-only, consistent with this project's existing never-hard-delete convention.