fix: show raw PHP response in error message, clean up errores column UI

- sync_paciente: catch JSONDecodeError separately and include HTTP status
  + first 300 chars of raw response so PHP errors are visible in the log
- envios_erp.html: Errores column shows count only (not all inline messages)
  — error detail is already visible in the expandable Ver N row

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/templates/envios_erp.html

@@ -311,9 +311,7 @@ async function cargarHistorialScheduler() {
                                 <td class="py-2 pr-3 text-right text-blue-600 font-medium">${r.created}</td>
                                 <td class="py-2 pr-3 text-right text-green-600">${r.updated}</td>
                                 <td class="py-2 pr-3 text-right ${r.errores > 0 ? 'text-red-500 font-medium' : 'text-gray-300'}">
-                                    ${r.errores > 0 && errDet.length
-                                        ? errDet.map(e => `<div class="text-red-600 text-xs">${e.doc} — ${e.msg}</div>`).join('')
-                                        : r.errores || '—'}
+                                    ${r.errores || '—'}
                                 </td>
                                 <td class="py-2 text-right">
                                     ${pacientes.length ? `