feat: add a read-only Mercado Pago account probe

Card payments with the test credentials are refused with 10111 and 10113,
which depend on the account behind the token. python -m
app.mercadopago_probe shows that account (and whether it is a test user),
the card methods it accepts, and how Mercado Pago classifies a card's first
digits: type, issuer and instalments. It creates and charges nothing.

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

app/mercadopago_probe.py

@@ -0,0 +1,68 @@
+"""Read-only look at the Mercado Pago account behind MP_ACCESS_TOKEN.
+
+    python -m app.mercadopago_probe [--bin 503143] [--valor 50]
+
+Run from the api container's console (Portainer > Containers > api >
+Console). It creates nothing and charges nothing: it asks Mercado Pago which
+account the token belongs to, which card methods the account accepts, and how
+it classifies a card number's first digits (type, issuer, instalments). That
+is what payment errors such as 10111 (issuer) and 10113 (method excluded by a
+rule) depend on.
+"""
+import argparse
+import os
+import sys
+
+import httpx
+
+from .core.secrets import load as load_secret_files
+
+API = 'https://api.mercadopago.com'
+
+
+def main(argv=None):
+    parser = argparse.ArgumentParser(prog='python -m app.mercadopago_probe')
+    parser.add_argument('--bin', default='503143', help="the card's first six digits (default: the Mastercard test card)")
+    parser.add_argument('--valor', default='50', help='amount in reais for the instalment lookup')
+    args = parser.parse_args(argv)
+    load_secret_files()
+    token = os.environ.get('MP_ACCESS_TOKEN', '')
+    if not token:
+        print('MP_ACCESS_TOKEN is not set in this container.')
+        return 1
+    http = httpx.Client(base_url=API, timeout=15, headers={'Authorization': f'Bearer {token}'})
+
+    print(f"Token: {'TEST' if token.startswith('TEST-') else 'produção'}")
+    me = http.get('/users/me')
+    if me.status_code == 200:
+        user = me.json()
+        tags = user.get('tags') or []
+        print(f"Conta: id {user.get('id')} · {user.get('nickname')} · site {user.get('site_id')} · "
+              f"usuário de teste: {'sim' if 'test_user' in tags else 'não'} · tags {tags}")
+    else:
+        print(f'Conta: HTTP {me.status_code} {me.text[:200]}')
+
+    methods = http.get('/v1/payment_methods')
+    if methods.status_code == 200:
+        cards = [m for m in methods.json() if m.get('payment_type_id') in ('credit_card', 'debit_card')]
+        print('Cartões aceitos pela conta:')
+        for m in cards:
+            print(f"  {m.get('id'):<12} {m.get('payment_type_id'):<12} {m.get('status')}")
+    else:
+        print(f'Meios de pagamento: HTTP {methods.status_code} {methods.text[:200]}')
+
+    quote = http.get('/v1/payment_methods/installments', params={'bin': args.bin, 'amount': args.valor})
+    if quote.status_code == 200 and quote.json():
+        print(f'BIN {args.bin}:')
+        for option in quote.json():
+            issuer = option.get('issuer') or {}
+            counts = [c.get('installments') for c in option.get('payer_costs') or []]
+            print(f"  meio {option.get('payment_method_id')} · tipo {option.get('payment_type_id')} · "
+                  f"emissor {issuer.get('id')} ({issuer.get('name')}) · parcelas {counts}")
+    else:
+        print(f'BIN {args.bin}: HTTP {quote.status_code} {quote.text[:300]}')
+    return 0
+
+
+if __name__ == '__main__':
+    sys.exit(main())