fix(ui): move mobile search bar to top to avoid keyboard occlusion

Moves the `#mobileSearchContainer` from the bottom-right corner to the top of the viewport (`top-4`). This ensures that the search input remains visible when the virtual keyboard is active on mobile devices, preventing it from being covered.

- Updated `index.html` to change classes from `bottom-6 right-6 origin-bottom-right` to `top-4 left-4 right-4 origin-top`.
- Removed `w-[calc(...)]` in favor of `left-4 right-4` for simpler full-width behavior with margins.
- Ran `npm run build:css` to update generated CSS.

index.html

@@ -379,7 +379,7 @@
       <!-- Mobile Search Container -->
       <div
         id="mobileSearchContainer"
-        class="fixed bottom-6 right-6 z-50 hidden w-[calc(100%-var(--sidebar-mobile-gutter))] max-w-sm origin-bottom-right transition-all duration-200 md:hidden"
+        class="fixed top-4 left-4 right-4 z-50 hidden max-w-sm mx-auto origin-top transition-all duration-200 md:hidden"
       >
         <form
           id="mobileSearchForm"