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/env_config_panel.html

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+{# env配置：按功能分组，三列卡片布局 #}
+<div class="env-config-page">
+    <div class="env-config-head card">
+        <h2>env 配置</h2>
+        <p class="settings-env-hint">读取并编辑本实例 <code>.env</code>。标注「保存即生效」的项会立即应用；标注「需重启」的项保存后请点「保存并重启」。</p>
+        <div class="env-config-toolbar">
+            <button type="button" class="btn-primary btn-sm" id="env-config-save">保存</button>
+            <button type="button" class="btn-secondary btn-sm" id="env-config-save-restart">保存并重启</button>
+            <button type="button" class="btn-secondary btn-sm" id="env-config-reload">重新加载</button>
+            <span class="settings-status-line" id="env-config-status"></span>
+        </div>
+    </div>
+    <div id="env-config-grid" class="env-config-grid">
+        <div class="env-config-loading muted">加载配置中…</div>
+    </div>
+</div>