refactor: 将情景图标和设备选择器的 emoji 统一替换为 SVG 图标

- 新增 scenarioIcons.tsx 提取情景图标渲染逻辑
- 情景芯片、设备选择器、警告提示等 emoji 全部改为 Feather-style SVG
- 调整 CSS 确保 SVG 图标居中对齐

frontend/src/components/SessionSidebar/index.tsx

@@ -187,7 +187,7 @@ export function SessionSidebar({
                         <>
                           {/* 视频标记图标 */}
                           {session.messageCount > 5 && (
-                            <span className="sidebar__item-icon" title={t("sidebar.video")}>📹</span>
+                            <span className="sidebar__item-icon" title={t("sidebar.video")}><svg width="12" height="12" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2" strokeLinecap="round" strokeLinejoin="round"><polygon points="23 7 16 12 23 17 23 7"/><rect x="1" y="5" width="15" height="14" rx="2" ry="2"/></svg></span>
                           )}
                           <div className="sidebar__item-content">
                             <div className="sidebar__item-title">{session.title}</div>
@@ -207,7 +207,7 @@ export function SessionSidebar({
                               }}
                               title={t("sidebar.rename")}
                             >
-                              ✏
+                              <svg width="14" height="14" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2" strokeLinecap="round" strokeLinejoin="round"><path d="M11 4H4a2 2 0 0 0-2 2v14a2 2 0 0 0 2 2h14a2 2 0 0 0 2-2v-7"/><path d="M18.5 2.5a2.121 2.121 0 0 1 3 3L12 15l-4 1 1-4 9.5-9.5z"/></svg>
                             </button>
                             <button
                               className="sidebar__action-btn sidebar__action-btn--danger"
@@ -217,7 +217,7 @@ export function SessionSidebar({
                               }}
                               title={t("sidebar.delete")}
                             >
-                              🗑
+                              <svg width="14" height="14" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2" strokeLinecap="round" strokeLinejoin="round"><polyline points="3 6 5 6 21 6"/><path d="M19 6v14a2 2 0 0 1-2 2H7a2 2 0 0 1-2-2V6m3 0V4a2 2 0 0 1 2-2h4a2 2 0 0 1 2 2v2"/></svg>
                             </button>
                           </div>
                         </>