Fix LE cert creation: use empty meta for NPM API compatibility

NPM's certificate creation endpoint rejects letsencrypt_agree and
letsencrypt_email in the meta field (schema validation error). The
LE email is configured globally in NPM settings. Empty meta works.

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

app/services/npm_service.py

@@ -343,10 +343,7 @@ async def _request_ssl(
     ssl_payload = {
         "domain_names": [domain],
         "provider": "letsencrypt",
-        "meta": {
-            "letsencrypt_agree": True,
-            "letsencrypt_email": admin_email,
-        },
+        "meta": {},
     }
     try:
         logger.info("Requesting Let's Encrypt certificate for %s (email: %s) ...", domain, admin_email)