Verified identity troubleshooting

• 403 verified_identity: entitlement/add-on not active.
• 400 secret not configured: tenant signing secret missing.
• 401 invalid bearer token: missing or invalid SETCHAT_SERVER_TOKEN.
• 400 invalid siteApiKey: invalid site key or inactive site.
• Anonymous visitor: token missing, expired, or not injected.
• Wrong mapping: unstable externalUserId across sessions.