fix(frontend): address review feedback on admin rate-limit components

- Replace legacy Button import and lucide Search icon with non-legacy
  Button and Phosphor MagnifyingGlass icon in AdminUserSearch
- Trim search query before submitting in AdminUserSearch.handleSearch
- Always set selectedUser with fallback when user_email is missing in
  RateLimitManager direct lookup
- Replace placeholder string with empty string for missing userEmail in
  AdminUserGrantHistory

autogpt_platform/frontend/src/app/(platform)/admin/components/AdminUserSearch.tsx

@@ -2,8 +2,8 @@
 
 import { useState } from "react";
 import { Input } from "@/components/__legacy__/ui/input";
-import { Button } from "@/components/__legacy__/ui/button";
-import { Search } from "lucide-react";
+import { Button } from "@/components/atoms/Button/Button";
+import { MagnifyingGlass } from "@phosphor-icons/react";
 
 export interface AdminUserSearchProps {
   /** Current search query value (controlled). Falls back to internal state if omitted. */
@@ -44,7 +44,7 @@ export function AdminUserSearch({
   }
 
   function handleSearch() {
-    onSearch(currentValue);
+    onSearch(currentValue.trim());
   }
 
   return (
@@ -58,10 +58,12 @@ export function AdminUserSearch({
       />
       <Button
         variant="outline"
+        size="small"
         onClick={handleSearch}
         disabled={isLoading || !currentValue.trim()}
+        loading={isLoading}
       >
-        {isLoading ? "Searching..." : <Search className="h-4 w-4" />}
+        {isLoading ? "Searching..." : <MagnifyingGlass size={16} />}
       </Button>
     </div>
   );

autogpt_platform/frontend/src/app/(platform)/admin/rate-limits/components/RateLimitManager.tsx

@@ -61,12 +61,10 @@ export function RateLimitManager() {
         throw new Error("Failed to fetch rate limit");
       }
       setRateLimitData(response.data);
-      if (response.data.user_email) {
-        setSelectedUser({
-          user_id: response.data.user_id,
-          user_email: response.data.user_email,
-        });
-      }
+      setSelectedUser({
+        user_id: response.data.user_id,
+        user_email: response.data.user_email ?? response.data.user_id,
+      });
     } catch (error) {
       console.error("Error fetching rate limit:", error);
       const hint = looksLikeEmail(trimmed)

autogpt_platform/frontend/src/app/(platform)/admin/spending/components/AdminUserGrantHistory.tsx

@@ -151,15 +151,11 @@ export async function AdminUserGrantHistory({
                     <div className="flex items-center justify-end gap-2">
                       <RateLimitModal
                         userId={transaction.user_id}
-                        userEmail={
-                          transaction.user_email ?? "User Email wasn't attached"
-                        }
+                        userEmail={transaction.user_email ?? ""}
                       />
                       <AdminAddMoneyButton
                         userId={transaction.user_id}
-                        userEmail={
-                          transaction.user_email ?? "User Email wasn't attached"
-                        }
+                        userEmail={transaction.user_email ?? ""}
                         currentBalance={transaction.current_balance}
                         defaultAmount={
                           transaction.transaction_type ===