feat(site): multi-site join server endpoints + persisted site role + emoji fix

Server endpoints for joining a spoke to a master directory (MULTI_SITE_SPEC.md).
This pass is server-only; setup.sh wiring and the UI are the next layer.

- Site join keys (SiteJoinKey model, stj_ prefix): mint/revoke/delete/list,
  hashed at rest, shown once — the same model as agent join keys.
- POST /api/site/export (master, Bearer stj_ key, no admin session): returns the
  local LDAP tree (slapcat LDIF) + resource catalog + siteSlug + baseDn.
- POST /api/site/join (spoke, admin): { masterUrl, joinKey } pulls the master
  export, imports resources (upsert by slug) + LDAP (ldapadd -c), and persists
  the spoke role. Refused if already a spoke.
- Persisted site role: utils/site_config.js keeps isMaster/masterUrl/siteSlug in
  /config/site.json (env seeds defaults); site-status/site-promote now use it.
- Unit tests (site_join, site_config) with in-memory stubs, wired into npm test.
- docs/site-join.md + docs router entry.
- Repairs the corrupted multi-site emojis (crown/bolt) in directory.ejs.
- .gitguardian.yml ignores the generic-password false positive on reading the
  LDAP bind credential from runtime config (never a hardcoded secret).

nodejs/routes/api_directory_admin.js

@@ -882,12 +882,11 @@ router.post('/discovered/merge', async (req, res, next) => {
 });
 
 // ── Multi-Site & Master Node Status Endpoints ────────────────────────────────
-let localSiteConfig = {
-  isMaster: process.env.IS_MASTER ? (process.env.IS_MASTER === 'true') : true,
-  masterUrl: process.env.MASTER_URL || '',
-  siteSlug: process.env.SITE_SLUG || 'site-default',
-  wanConnected: true
-};
+// The site role (master/spoke, site slug, master URL) is persisted by
+// utils/site_config.js so it survives restarts; the env vars IS_MASTER /
+// MASTER_URL / SITE_SLUG only seed the defaults. site-promote and the
+// /api/site/join flow both write to it.
+const siteConfig = require('../utils/site_config');
 
 router.get('/site-status', async (req, res, next) => {
   try {
@@ -895,14 +894,15 @@ router.get('/site-status', async (req, res, next) => {
     const allResources = await Resource.list();
     const gateResources = allResources.filter(r => r.metadata && r.metadata.subType === 'wireguard');
 
+    const cfg = siteConfig.get();
     res.json({
       status: 'ok',
       config: {
-        isMaster: localSiteConfig.isMaster,
-        masterUrl: localSiteConfig.masterUrl,
-        siteSlug: localSiteConfig.siteSlug,
-        wanConnected: localSiteConfig.wanConnected,
-        siteMode: localSiteConfig.isMaster ? 'master' : 'spoke'
+        isMaster: cfg.isMaster,
+        masterUrl: cfg.masterUrl,
+        siteSlug: cfg.siteSlug,
+        wanConnected: cfg.wanConnected,
+        siteMode: cfg.isMaster ? 'master' : 'spoke'
       },
       sitesCount: sites.length,
       sites: sites.map(s => ({ id: s.id, name: s.name, slug: s.slug })),
@@ -920,18 +920,18 @@ router.post('/site-promote', async (req, res, next) => {
       return res.status(403).json({ status: 'error', message: 'Master promotion requires explicit god_admin authority' });
     }
 
-    localSiteConfig.isMaster = true;
-    localSiteConfig.masterUrl = '';
-    
+    siteConfig.save({ isMaster: true, masterUrl: '' });
+
     console.log(`[MULTI-SITE] Node promoted to MASTER by user ${req.user ? req.user.uid : 'admin'}`);
 
+    const cfg = siteConfig.get();
     res.json({
       status: 'ok',
       message: 'Node successfully promoted to Master Site',
       config: {
         isMaster: true,
         masterUrl: '',
-        siteSlug: localSiteConfig.siteSlug,
+        siteSlug: cfg.siteSlug,
         siteMode: 'master'
       }
     });