ui(mobile): block pinch-zoom and iOS input auto-zoom

- index.html: tighten the viewport meta with maximum-scale=1,
  user-scalable=no, viewport-fit=cover so pinch-zoom is disabled
  on browsers that honor the hint (Android Chrome).
- SearchPanel: bump the mobile search input from text-sm (14px) to
  text-base (16px). iOS Safari auto-zooms inputs whose font-size is
  below 16px on focus, which widened the viewport and let the user
  pan horizontally; 16px stops that behavior at the source.

src/components/SearchPanel.tsx

@@ -148,7 +148,7 @@ export function SearchPanel({
               onChange={(e) => onQueryChange(e.target.value)}
               onKeyDown={(e) => e.key === "Enter" && onSearch()}
               placeholder={t("searchPanelPlaceholder")}
-              className="min-w-0 flex-1 bg-transparent text-sm text-neutral-100 outline-none placeholder:text-[#777985]"
+              className="min-w-0 flex-1 bg-transparent text-base text-neutral-100 outline-none placeholder:text-[#777985]"
             />
             <button
               type="button"