feat(ui): theme & layout improvements

- Dark-blue theme background assets and styling integration
- Appearance settings with layoutMode (full/compact) preference
- Settings dialog and auth context updates
- AI writing form and panel refinements
- Open Canvas context updates
- Roundtable planning styling and dashboard enhancements
- Strategy components and header updates
- Light app management and routing improvements
- Global style enhancements for dark theme
- Various page layout and workspace routing optimizations

frontend-web/src/strategy-components/components/task-components/css/strategy-data.css

@@ -25,7 +25,7 @@
   --color-main: var(--color-primary);
   --td-brand-color: var(--color-primary);
   --bg-color: rgba(22, 119, 255, 0.12);
-  --card-border: rgba(110, 136, 176, 0.32);
+  --card-border: rgba(43, 143, 254, 0.55);
   --text-color: var(--color-text-strong);
 
   --card-bg: 220 59% 16%;
@@ -33,6 +33,14 @@
   --border-color: 220 54% 29%;
   --input-bg: 220 71% 10%;
   --input-border: 220 35% 38%;
+
+  /* 深色背景图：对齐多智能体会商页风格，fixed 固定不随内容滚动 */
+  background-image: url("../../../../assets/img/layout-bg-theme-dark-blue.svg");
+  background-size: cover;
+  background-position: center top;
+  background-repeat: no-repeat;
+  background-attachment: fixed;
+  background-color: #0c1836;
 }
 
 /* ── Theme card (TaskCard, KanbanColumn) ─────────────────────────────── */