fix vault 403 + shared secrets (v1.21.0)

- vault_broker: always reconcile policy content before serving a cached
  token (compare-and-skip), so stale stored policies can't cause a recurring
  403 'permission denied'; policy content is parsed live by OpenBao, so edits
  apply to existing tokens immediately.
- Shared secrets: publish to secret/shared/<owner>/<slug>; grant read to users
  and apps by editing the grantee's policy content (live-applied). New
  SharedSecret/SharedSecretGrant ORM models, /api/shared-secrets router, and a
  Shared tab in the vault UI.
- package.json + lockfile bumped to 1.21.0 to match the tag.

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

nodejs/models/index.js

@@ -17,6 +17,8 @@ const { Resource, ResourceEdge, ResourceGroup } = require('./resource');
 const { AccessRequest } = require('./access_request');
 const { Webhook } = require('./webhook');
 const { PluginInstance } = require('./plugin_instance');
+const { SharedSecret } = require('./shared_secret');
+const { SharedSecretGrant } = require('./shared_secret_grant');
 async function initORM() {
   const ormConf = conf.orm || {
     dialect: 'sqlite',
@@ -31,6 +33,7 @@ async function initORM() {
       conf: { orm: ormConf },
       models: [
         Resource, ResourceEdge, ResourceGroup, AccessRequest, Webhook, PluginInstance,
+        SharedSecret, SharedSecretGrant,
         Token, AuthToken, InviteToken, ImpersonationToken, PasswordResetToken, OtpToken, ServiceToken
       ]
     });