feat: support configurable Shulam facilitator URL for compliance screening

[shulam-pay]

Summary

Add support for a configurable Shulam facilitator URL so that Bankr users can point compliance screening and trust scoring at custom deployments (e.g., bankr.shulam.xyz for operator-attributed requests).

Motivation

Currently the Shulam API URL is hardcoded to https://api.shulam.xyz. For Bankr's white-label integration, requests should route through https://bankr.shulam.xyz to enable:

• Operator attribution — all screenings and transactions are tracked under Bankr's operator account
• Custom compliance thresholds — Bankr-specific hold/block thresholds (0.50/0.95)
• Metering — usage tracking per operator for billing
• Event routing — bankr.operator.* events emitted for Bankr-specific monitoring

Proposed Changes

1. Environment variable: Add SHULAM_FACILITATOR_URL (default: https://api.shulam.xyz)
2. Config surface: Allow setting via .env, CLI flag, or runtime config
3. Affected endpoints:
   • POST /v1/compliance/screen — compliance screening
   • GET /v1/trust/score/:address — trust scoring
   • POST /verify — EIP-3009 payment verification
   • POST /settle — on-chain settlement

Example

# .env
SHULAM_FACILITATOR_URL=https://bankr.shulam.xyz
SHULAM_API_KEY=sk_live_bankr_...

import { screenWallet } from '@shulam/compliance-screening';

const result = await screenWallet('0x...', {
  apiUrl: process.env.SHULAM_FACILITATOR_URL,
  apiKey: process.env.SHULAM_API_KEY,
});

Acceptance Criteria

• SHULAM_FACILITATOR_URL env var accepted, defaults to https://api.shulam.xyz
• All Shulam API calls use the configured URL
• README documents the configuration option
• Tests verify custom URL routing

Related

• Shulam PL-9: Bankr Code Integration (E-BCI-06)
• bankr-skills/compliance-screening/ — uses SHULAM_API_URL config
• bankr-skills/trust-scoring/ — uses SHULAM_API_URL config