Add instance nav prefs, env config UI, and PM2 restart.

P1-P4: configurable nav/section visibility in system settings, full .env editor with restart badges, password change, runtime hot overrides, and single-instance pm2 restart. Works in hub embed iframe.
Co-authored-by: Cursor <cursoragent@cursor.com>

lib/instance/templates/embed_page_fragment.html

@@ -396,6 +396,9 @@
         </div>
         {% endif %}
 </div>
+    {% if page == 'env_config' %}
+    {% include 'env_config_panel.html' %}
+    {% endif %}
     {% if page == 'risk_policy' %}
     {% include 'risk_policy_panel.html' %}
     {% endif %}