fix: 暗黑模式UI优化 — 导航栏/页面背景互换, Element Plus组件适配, 亮灯表卡片+仪表盘图标暗色适配

- 极简/科技深色: 导航栏和页面背景颜色互换(sidebar更亮,page更暗)
- 新增20+条 Element Plus 暗色全局覆盖(input/select/table/pagination/button/dialog/tabs/date-picker等)
- Dashboard: stat-glyph在暗色下移除背景色(参考本周请假), progress-row背景降低亮度
- LightBoard: 卡片文字固定深色(card背景是浅色), light-dot适配暗色背景
- 新增 --c-bg-light token 防止暗色下summary-bar回退到浅色

Co-Authored-By: Claude <noreply@anthropic.com>

frontend/src/views/desktop/Dashboard.vue

@@ -426,4 +426,17 @@ function rowState(p: any): 'full' | 'catching' | 'missing' | 'on_leave' | 'rest_
 .leave-text { font-size: 13px; color: #5B7FA5; font-family: var(--font-body); }
 .rest-text { font-size: 13px; color: #9CA3AF; font-family: var(--font-body); }
 .empty { text-align: center; color: var(--c-text-muted); padding: 40px 0; font-family: var(--font-body); }
+
+/* ═══ Dark Mode — Dashboard ═══ */
+html.dark .stat-glyph--ink,
+html.dark .stat-glyph--sage,
+html.dark .stat-glyph--gold,
+html.dark .stat-glyph--vermilion {
+  background: transparent;
+}
+html.dark .progress-row--missing  { background: rgba(248,113,113,0.06); }
+html.dark .progress-row--catching { background: rgba(251,191,36,0.05); }
+html.dark .progress-row--full     { background: rgba(74,222,128,0.05); }
+html.dark .progress-row--on_leave { background: rgba(96,165,250,0.05); }
+html.dark .progress-row--rest_day { background: rgba(156,163,175,0.03); }
 </style>