feat(loyalty): pair POS terminal devices with one-time setup QR

Adds the backend half of the Android tablet rollout. Merchants can
pair tablets to specific stores from /merchants/loyalty/devices (or
admins can pair on behalf from the merchant detail page). Each
pairing issues a long-lived JWT shown ONCE in the response with a
server-rendered QR PNG containing {api_url, store_code, auth_token} —
the tablet scans it on first boot and persists the three fields.

The store API (/api/v1/store/loyalty/*) now accepts these device JWTs
alongside user JWTs. Revoking a device row immediately rejects its
token (401 TERMINAL_DEVICE_REVOKED). Tokens expire after 1 year;
re-pair to renew.

- Migration loyalty_010 + TerminalDevice model
- create_device_token / verify_device_token JWT helpers
- 5 endpoints x 2 portals (merchant + admin on-behalf)
- Bearer-auth wiring in app/api/deps.py
- Pages, shared list partial with one-time pairing-QR modal,
  Alpine.js factories
- Locale strings (en authoritative; fr/de/lb seeded with EN copy
  for translation)
- 6 integration tests covering pair, list, revoke, idempotency,
  cross-merchant rejection, store-API auth via device JWT

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

app/modules/loyalty/static/merchant/js/loyalty-devices.js

@@ -0,0 +1,16 @@
+// app/modules/loyalty/static/merchant/js/loyalty-devices.js
+const merchantDevicesLog = window.LogConfig.loggers.merchantDevices || window.LogConfig.createLogger('merchantDevices');
+
+function merchantLoyaltyDevices() {
+    return loyaltyDevicesList({
+        apiPrefix: '/merchants/loyalty',
+        showStoreFilter: true,
+        showCrud: true,
+        currentPage: 'devices',
+    });
+}
+
+if (!window.LogConfig.loggers.merchantDevices) {
+    window.LogConfig.loggers.merchantDevices = window.LogConfig.createLogger('merchantDevices');
+}
+merchantDevicesLog.info('Merchant loyalty devices module loaded');