feat: add a read-only Jadlog price probe

app/jadlog.py prices one package through Jadlog's Simulador de Frete as the
API manual v2.3 describes it; app.jadlog_probe prices test weights to six
regions on the client's account to confirm token, account and contract.
Tested against a fake transport. The roadmap records the Jadlog data and the
Mercado Pago account setup.

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

docs/ROADMAP.md

@@ -247,9 +247,24 @@ From the report already sent. These are dated promises, not backlog.
   quote cannot be charged twice. The Site CSP gains the Mercado Pago origins
   only through `PAYMENT_CSP_SOURCES`, empty by default. Not yet rendered
   against a real public key; sandbox run and refund policy remain.
+  **Account setup (2026-09-28):** the client's application is Checkout
+  Transparente on the Payments API, webhook event "Pagamentos (legacy)" only,
+  URL `https://dtf.agenciacompor.com.br/api/payments/webhook`. The production
+  compose now takes `PAYMENT_ADAPTER` and `MP_*` from Portainer (it hard-coded
+  the fake adapter), so the sandbox runs on production with test credentials;
+  the Site has no real customers yet. A verified notification whose payment
+  does not exist (the panel's "Simular notificação") is acknowledged instead
+  of answering 500, which would have made Mercado Pago retry it.
 - `[ ]` 1.2 — Real freight quotation. **Blocked on client inputs** (see
   `PRODUCTION_INPUTS.md`): source platform, credentials, origin CEP, services,
   packaging weight/dimensions per length, subsidy policy.
+  **Received (2026-09-25):** Jadlog, API access (user/CNPJ, client code,
+  token, account), origin CEP 14402-310, service .PACKAGE (modalidade 3),
+  home delivery, billed by contract. Still missing: packaging weight and
+  dimensions per length and how freight is charged to the customer (asked
+  2026-09-28). `app/jadlog.py` prices one package from the manual (v2.3);
+  `python -m app.jadlog_probe` prices test weights to six regions, read-only,
+  to confirm token, account and contract on the client's account. Not yet run.
 - `[~]` 1.3 — Idempotent Tiny/Olist order creation with order-number traceability.
   Confirm endpoints, tag behaviour and rate limits first.
   **Groundwork (2026-09-24), API v3 by decision:** OAuth2 against Tiny's