feat(desktop): add search autocomplete to desktop header

The desktop header search only navigated on submit — the autocomplete
suggestions dropdown existed on mobile (explore SearchSection) but was
never wired into the desktop chrome. Reuse the same useSearchAutocomplete
hook (debounced) and render a suggestions dropdown under the search box:
product titles navigate to /search, sellers navigate to /seller/<id>.
Closes on outside-click / Escape / selection.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app/components/desktop/DesktopHeader.tsx

@@ -1,9 +1,12 @@
 import { Link, useLocation, useNavigate } from "@remix-run/react";
-import { useState, type FormEvent } from "react";
-import { Search, Heart, ShoppingBag, User } from "lucide-react";
+import { useState, useRef, useEffect, type FormEvent } from "react";
+import { Search, Heart, ShoppingBag, User, Store } from "lucide-react";
 import { useRootData } from "~/hooks/use-root-data";
 import { useCartCount } from "~/requestHandler/use-cart-hooks";
+import { useSearchAutocomplete } from "~/requestHandler/use-search-hooks";
+import { useDebounce } from "~/hooks/useDebounce";
 import { SunMoonToggle } from "~/components/SunMoonToggle";
+import { AutocompleteSuggestionTypeEnum } from "../../../src/api/types";
 import logo from "~/assets/logo/SVG-07.svg";
 
 const NAV = [
@@ -23,15 +26,54 @@ const DesktopHeader = () => {
   const { user, theme } = useRootData();
   const cartCount = useCartCount();
   const [q, setQ] = useState("");
+  const [open, setOpen] = useState(false);
+  const searchRef = useRef<HTMLDivElement>(null);
   const isLoggedIn = !!user?.access_token;
 
+  const debouncedQ = useDebounce(q.trim(), 400);
+  const { data: autocompleteData, isLoading: isSuggesting } =
+    useSearchAutocomplete(debouncedQ);
+  const suggestions = autocompleteData?.suggestions ?? [];
+  const showSuggestions = open && q.trim().length > 0;
+
+  // Close the suggestions dropdown when clicking outside the search box.
+  useEffect(() => {
+    const onClickOutside = (e: MouseEvent) => {
+      if (searchRef.current && !searchRef.current.contains(e.target as Node)) {
+        setOpen(false);
+      }
+    };
+    document.addEventListener("mousedown", onClickOutside);
+    return () => document.removeEventListener("mousedown", onClickOutside);
+  }, []);
+
   const isActive = (to: string) =>
     to === "/" ? location.pathname === "/" : location.pathname.startsWith(to);
 
+  const goToSearch = (term: string) => {
+    const t = term.trim();
+    if (!t) return;
+    setOpen(false);
+    navigate(`/search/${encodeURIComponent(t)}`);
+  };
+
   const onSearch = (e: FormEvent) => {
     e.preventDefault();
-    const term = q.trim();
-    if (term) navigate(`/search/${encodeURIComponent(term)}`);
+    goToSearch(q);
+  };
+
+  const onSelectSuggestion = (sug: {
+    type: AutocompleteSuggestionTypeEnum;
+    text?: string;
+    name?: string;
+    id?: string;
+  }) => {
+    if (sug.type === AutocompleteSuggestionTypeEnum.Seller && sug.id) {
+      setOpen(false);
+      navigate(`/seller/${sug.id}`);
+      return;
+    }
+    goToSearch(sug.text || sug.name || "");
   };
 
   return (
@@ -61,21 +103,80 @@ const DesktopHeader = () => {
           ))}
         </nav>
 
+        <div ref={searchRef} className="flex-1 max-w-[460px] mx-auto relative">
           <form
             onSubmit={onSearch}
-          className="flex-1 max-w-[460px] mx-auto flex items-center gap-2.5 bg-WHITE3 border border-transparent rounded-xl px-3.5 h-11 transition-colors focus-within:bg-WHITE focus-within:border-GRAY3"
+            className="flex items-center gap-2.5 bg-WHITE3 border border-transparent rounded-xl px-3.5 h-11 transition-colors focus-within:bg-WHITE focus-within:border-GRAY3"
           >
             <Search size={20} className="text-GRAY shrink-0" />
             <input
               value={q}
-            onChange={(e) => setQ(e.target.value)}
+              onChange={(e) => {
+                setQ(e.target.value);
+                setOpen(true);
+              }}
+              onFocus={() => setOpen(true)}
+              onKeyDown={(e) => {
+                if (e.key === "Escape") setOpen(false);
+              }}
               name="q"
+              autoComplete="off"
               placeholder="جستجوی محصول، برند یا فروشگاه…"
               aria-label="جستجو"
               className="w-full bg-transparent outline-none text-[14.5px] text-BLACK placeholder:text-GRAY"
             />
           </form>
 
+          {showSuggestions ? (
+            <div
+              dir="rtl"
+              className="absolute top-full inset-x-0 mt-2 max-h-[360px] overflow-y-auto rounded-xl bg-WHITE border border-WHITE3 shadow-xl py-1.5 z-50"
+            >
+              {isSuggesting && suggestions.length === 0 ? (
+                <p className="px-4 py-3 text-[13px] text-GRAY">در حال جستجو...</p>
+              ) : suggestions.length > 0 ? (
+                suggestions.map((sug, index) => {
+                  const isSeller =
+                    sug.type === AutocompleteSuggestionTypeEnum.Seller;
+                  const label = isSeller ? sug.name : sug.text;
+                  if (!label) return null;
+                  return (
+                    <button
+                      key={`${sug.type}-${sug.id ?? sug.text ?? index}`}
+                      type="button"
+                      onClick={() => onSelectSuggestion(sug)}
+                      className="w-full flex items-center gap-2.5 px-4 h-11 text-right hover:bg-WHITE2 transition-colors"
+                    >
+                      {isSeller ? (
+                        <Store size={17} className="text-GRAY shrink-0" />
+                      ) : (
+                        <Search size={17} className="text-GRAY shrink-0" />
+                      )}
+                      <span className="text-[14px] text-BLACK truncate">
+                        {label}
+                      </span>
+                      {isSeller ? (
+                        <span className="mr-auto text-[11px] text-GRAY shrink-0">
+                          فروشگاه
+                        </span>
+                      ) : null}
+                    </button>
+                  );
+                })
+              ) : (
+                <button
+                  type="button"
+                  onClick={() => goToSearch(q)}
+                  className="w-full flex items-center gap-2.5 px-4 h-11 text-right hover:bg-WHITE2 transition-colors"
+                >
+                  <Search size={17} className="text-GRAY shrink-0" />
+                  <span className="text-[14px] text-BLACK truncate">{q}</span>
+                </button>
+              )}
+            </div>
+          ) : null}
+        </div>
+
         <div className="flex items-center gap-2.5 shrink-0">
           <SunMoonToggle theme={theme} />
           {isLoggedIn ? (