style(ui): 添加梦幻视觉效果和优化话题卡片样式

- 新增梦幻发光效果变量和动画实现
- 为主题背景添加浮动光晕装饰元素
- 重构话题卡片渐变背景和交互效果
- 实现卡片悬停时的平滑变换动画
- 添加响应式设计和可访问性支持
- 优化主题样式层级和渲染性能

scss/main.scss

@@ -2,6 +2,9 @@
 
 :root {
   --main-grid-gap: 0.5em;
+  --dream-glow-a: oklch(from var(--accent-color) calc(l * 1.08) calc(c * 0.45) h / 0.18);
+  --dream-glow-b: oklch(from var(--accent-color) calc(l * 1.2) calc(c * 0.35) calc(h + 26deg) / 0.14);
+  --dream-glow-c: oklch(from var(--accent-color) calc(l * 0.95) calc(c * 0.4) calc(h - 20deg) / 0.12);
 }
 
 html:not(:has(.has-full-page-chat)) {
@@ -14,12 +17,72 @@ html:not(:has(.has-full-page-chat)) {
 
 body {
   -webkit-font-smoothing: antialiased;
+  position: relative;
 
   @include viewport.until(sm) {
     background-color: var(--d-content-background);
   }
 }
 
+body:not(.has-full-page-chat, .wizard)::before,
+body:not(.has-full-page-chat, .wizard)::after {
+  content: "";
+  position: fixed;
+  width: min(42vw, 32rem);
+  aspect-ratio: 1 / 1;
+  border-radius: 999px;
+  filter: blur(48px);
+  pointer-events: none;
+  z-index: 0;
+}
+
+body:not(.has-full-page-chat, .wizard)::before {
+  top: 5rem;
+  left: -8rem;
+  background: radial-gradient(circle at 30% 30%, var(--dream-glow-a), transparent 65%);
+  animation: dreamy-float-a 18s ease-in-out infinite alternate;
+}
+
+body:not(.has-full-page-chat, .wizard)::after {
+  right: -6rem;
+  bottom: 2rem;
+  background: radial-gradient(circle at 65% 35%, var(--dream-glow-b), transparent 62%);
+  animation: dreamy-float-b 22s ease-in-out infinite alternate;
+}
+
+.d-header-wrap,
+#main-outlet-wrapper,
+.sidebar-wrapper,
+.sidebar-hamburger-dropdown {
+  position: relative;
+  z-index: 1;
+}
+
+@keyframes dreamy-float-a {
+  from {
+    transform: translate3d(0, 0, 0) scale(1);
+  }
+  to {
+    transform: translate3d(3rem, -1.5rem, 0) scale(1.08);
+  }
+}
+
+@keyframes dreamy-float-b {
+  from {
+    transform: translate3d(0, 0, 0) scale(1);
+  }
+  to {
+    transform: translate3d(-2.5rem, 2rem, 0) scale(1.1);
+  }
+}
+
+@media (prefers-reduced-motion: reduce) {
+  body:not(.has-full-page-chat, .wizard)::before,
+  body:not(.has-full-page-chat, .wizard)::after {
+    animation: none;
+  }
+}
+
 #main-outlet-wrapper {
   gap: var(--main-grid-gap);
 }

scss/topic-cards.scss

@@ -4,6 +4,17 @@
   --d-border-radius-small: calc(var(--d-border-radius) * 0.5);
 }
 
+@keyframes dreamy-card-shimmer {
+  from {
+    transform: translateX(-18%);
+    opacity: 0.35;
+  }
+  to {
+    transform: translateX(18%);
+    opacity: 0.65;
+  }
+}
+
 .topic-list .topic-list-item-separator {
   display: none;
 }
@@ -68,7 +79,12 @@
 
 .topic-list-body .topic-list-item {
   position: relative;
-  background: linear-gradient(45deg, var(--d-sidebar-active-background), #ffffff63);
+  background:
+    linear-gradient(
+      135deg,
+      oklch(from var(--d-content-background) calc(l * 0.995) c h) 0%,
+      oklch(from var(--d-content-background) calc(l * 1.02) calc(c * 0.65) h) 100%
+    );
   box-shadow:
     0 10px 30px -18px rgb(10 18 35 / 38%),
     0 6px 16px -10px var(--topic-card-shadow);
@@ -83,8 +99,11 @@
   grid-gap: var(--space-3);
   border-radius: var(--d-border-radius);
   cursor: pointer;
+  overflow: hidden;
   transition:
-    all 0.2s ease;
+    box-shadow 0.25s ease,
+    transform 0.25s ease,
+    background-color 0.25s ease;
 
   &::before {
     content: "";
@@ -92,10 +111,40 @@
     inset: 0;
     border-radius: inherit;
     padding: 1px;
+    background:
+      radial-gradient(
+        120% 100% at 0% 0%,
+        oklch(from var(--accent-color) calc(l * 1.15) calc(c * 0.5) h / 0.42),
+        transparent 56%
+      ),
+      radial-gradient(
+        120% 90% at 100% 100%,
+        oklch(from var(--accent-color) calc(l * 1.08) calc(c * 0.42) calc(h + 18deg) / 0.28),
+        transparent 58%
+      );
+    -webkit-mask:
+      linear-gradient(#000 0 0) content-box,
+      linear-gradient(#000 0 0);
+    -webkit-mask-composite: xor;
     mask-composite: exclude;
     pointer-events: none;
   }
 
+  &::after {
+    content: "";
+    position: absolute;
+    inset: -35% -20%;
+    background: linear-gradient(
+      112deg,
+      transparent 30%,
+      oklch(from var(--accent-color) calc(l * 1.16) calc(c * 0.28) h / 0.1) 48%,
+      transparent 66%
+    );
+    pointer-events: none;
+    mix-blend-mode: screen;
+    animation: dreamy-card-shimmer 9s ease-in-out infinite alternate;
+  }
+
   &.has-replies {
     grid-template-areas:
       "creator title title title status"
@@ -155,9 +204,11 @@
 
   &:hover {
     .discourse-no-touch & {
-      background: var(--d-sidebar-active-background);
-      box-shadow: 4px 5px 3px 1px #0003, 0 8px 20px -10px var(--topic-card-shadow);
-      border-left: 5px solid var(--d-button-danger-icon-color);
+      background: oklch(from var(--d-content-background) calc(l * 1.03) calc(c * 0.75) h);
+      box-shadow:
+        0 16px 34px -18px rgb(10 18 35 / 45%),
+        0 8px 20px -10px var(--topic-card-shadow);
+      transform: translateY(-2px);
     }
   }