feat: 主题选择改为标题栏调色盘

- 移除配置页的 select 下拉和面板外观卡片
- 在 header ❌ 左侧添加 4 个彩色圆点（赤红/青蓝/琥珀/紫雾）
- 圆点 hover 发光，active 白色边框高亮
- 汉化主题名称为 title 提示

panel.html

@@ -7,6 +7,12 @@
         <span>ST-BME 记忆图谱</span>
         <span class="bme-panel-subtitle" id="bme-panel-status">SYSTEM_ACTIVE</span>
       </div>
+      <div class="bme-theme-palette">
+        <button class="bme-theme-dot" data-theme="crimson" title="赤红" style="--dot-color: #e94560"></button>
+        <button class="bme-theme-dot" data-theme="cyan" title="青蓝" style="--dot-color: #00e5ff"></button>
+        <button class="bme-theme-dot" data-theme="amber" title="琥珀" style="--dot-color: #ffb300"></button>
+        <button class="bme-theme-dot" data-theme="violet" title="紫雾" style="--dot-color: #b388ff"></button>
+      </div>
       <button class="bme-panel-close" id="bme-panel-close" title="关闭">
         <i class="fa-solid fa-xmark"></i>
       </button>
@@ -353,18 +359,7 @@
               </details>
             </div>
 
-            <div class="bme-config-card">
-              <div class="bme-section-header">面板外观</div>
-              <div class="bme-config-row">
-                <label for="bme-setting-panel-theme">面板主题</label>
-                <select id="bme-setting-panel-theme" class="bme-config-input">
-                  <option value="crimson">Crimson Synth</option>
-                  <option value="cyan">Neon Cyan</option>
-                  <option value="amber">Amber Console</option>
-                  <option value="violet">Violet Haze</option>
-                </select>
-              </div>
-            </div>
+
           </div>
         </div>
       </div>