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/components/page-sdebar.css

@@ -379,6 +379,13 @@
     overflow-y: hidden;
 }
 
+/* 左右分组：不撑满、不裁切选中高光 */
+.top-submenu-bar--group {
+    flex: 0 0 auto;
+    margin-left: 0;
+    overflow: visible;
+}
+
 .top-submenu-list {
     min-width: max-content;
     height: 64px;
@@ -398,48 +405,31 @@
     border: 0;
     padding: 0 18px;
     background: transparent;
-    color: rgba(224, 242, 255, 0.9);
+    color: rgba(255, 255, 255, 0.8);
     font-family: "Source Han Sans SC", "Noto Sans SC", "Noto Sans S Chinese", "Microsoft YaHei", sans-serif;
-    font-size: 16px;
+    font-size: 18px;
     line-height: 1;
     font-weight: 700;
     letter-spacing: 0;
     white-space: nowrap;
     cursor: pointer;
-    overflow: hidden;
-    transition: color 0.18s ease, text-shadow 0.18s ease, background 0.18s ease;
+    overflow: visible;
+    transition: color 0.18s ease, text-shadow 0.18s ease;
 }
 
-.top-submenu-item:hover,
+.top-submenu-item:hover {
+    color: #9fe3ff;
+    text-shadow: 0 0 10px rgba(91, 210, 255, 0.4);
+}
+
+/* 选中态：设计稿提供的 nav-active.svg 发光高光 + 青色文字 */
 .top-submenu-item--active {
-    color: #ffffff;
-    text-shadow: 0 0 10px rgba(91, 210, 255, 0.45);
-    background:
-        linear-gradient(135deg, rgba(15, 84, 169, 0.52) 0%, rgba(5, 43, 103, 0.34) 76%),
-        linear-gradient(180deg, rgba(39, 126, 230, 0.2) 0%, rgba(0, 50, 122, 0.26) 100%);
-    box-shadow: inset 0 1px 0 rgba(98, 180, 255, 0.16), inset 0 -18px 22px rgba(0, 31, 79, 0.24);
-}
-
-.top-submenu-item--active::before {
-    content: '';
-    position: absolute;
-    left: 0;
-    right: 0;
-    bottom: 0;
-    height: 2px;
-    background: linear-gradient(90deg, rgba(59, 162, 255, 0) 0%, #35d7ff 50%, rgba(59, 162, 255, 0) 100%);
-    box-shadow: 0 0 12px rgba(53, 215, 255, 0.9), 0 -6px 18px rgba(33, 143, 255, 0.36);
-}
-
-.top-submenu-item--active::after {
-    content: '';
-    position: absolute;
-    left: 16px;
-    right: 16px;
-    bottom: 0;
-    height: 16px;
-    background: radial-gradient(ellipse at bottom, rgba(37, 189, 255, 0.34) 0%, rgba(37, 189, 255, 0) 68%);
-    pointer-events: none;
+    color: #64cdf5;
+    text-shadow: 0 0 12px rgba(100, 205, 245, 0.5);
+    background-image: url("../assets/img/nav-active.svg");
+    background-repeat: no-repeat;
+    background-position: center calc(50% + 7px);
+    background-size: 152px 42px;
 }
 
 .third-submenu-bar {