docs: fix mobile navbar (#55)

Author: idosal

docs/src/.vitepress/theme/custom.css

@@ -239,20 +239,17 @@ div[class*='language-'] code {
 }
 
 /* Enhanced navigation */
-.VPNav {
+.VPNavBar {
   backdrop-filter: blur(12px);
   background: rgba(255, 255, 255, 0.85);
   border-bottom: 1px solid var(--vp-c-divider);
+  box-shadow: var(--vp-shadow-1);
 }
 
-.dark .VPNav {
+.dark .VPNavBar {
   background: rgba(26, 26, 26, 0.85);
 }
 
-.VPNavBar {
-  box-shadow: var(--vp-shadow-1);
-}
-
 /* Enhanced sidebar */
 .VPSidebar {
   background: var(--vp-c-bg-soft);