docs: optimize home page styles (#18539)

Author: warmthsea

.vitepress/theme/styles/landing.css

@@ -4,13 +4,16 @@
 
 html:has(.landing) {
   background-color: #101010;
-  --vp-c-bg: #101010;
 
   body {
     background-color: #101010;
   }
 }
 
+html.dark:has(.landing) {
+  --vp-c-bg: #101010;
+}
+
 .landing {
   overflow-x: hidden;
   background-color: #101010;
@@ -37,9 +40,14 @@ html:has(.landing) {
 
     .content-body {
       background: none !important;
+      transition: none;
     }
   }
 
+  .VPNavBar *:not(.wrapper *) {
+    transition: none;
+  }
+
   .VPFooter {
     border-top: 1px solid #262626 !important;
     background: radial-gradient(circle at top center, #0f151a 30%, #000000 80%);
@@ -58,6 +66,10 @@ html:has(.landing) {
     display: none;
   }
 
+  .VPMenu .translations + .group {
+    display: none;
+  }
+
   .VPNavScreenAppearance {
     visibility: hidden;
   }