feat(06-03): update display components to use categoryIcon with LucideIcon

- Rename categoryEmoji to categoryIcon in ItemCard, CandidateCard, ThreadCard, ItemPicker
- Import and render LucideIcon at appropriate sizes (36px placeholder, 14-16px badges)
- Update hook interfaces to match server API (categoryIcon instead of categoryEmoji)
- Rename iconData.ts to iconData.tsx (contains JSX)
- Update useCategories mutation type to use icon instead of emoji

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/client/components/ThreadCard.tsx

@@ -1,5 +1,6 @@
 import { useNavigate } from "@tanstack/react-router";
 import { formatPrice } from "../lib/formatters";
+import { LucideIcon } from "../lib/iconData";
 
 interface ThreadCardProps {
 	id: number;
@@ -10,7 +11,7 @@ interface ThreadCardProps {
 	createdAt: string;
 	status: "active" | "resolved";
 	categoryName: string;
-	categoryEmoji: string;
+	categoryIcon: string;
 }
 
 function formatDate(iso: string): string {
@@ -36,7 +37,7 @@ export function ThreadCard({
 	createdAt,
 	status,
 	categoryName,
-	categoryEmoji,
+	categoryIcon,
 }: ThreadCardProps) {
 	const navigate = useNavigate();
 
@@ -66,7 +67,7 @@ export function ThreadCard({
 			</div>
 			<div className="flex flex-wrap gap-1.5">
 				<span className="inline-flex items-center px-2 py-0.5 rounded-full text-xs font-medium bg-blue-50 text-blue-700">
-					{categoryEmoji} {categoryName}
+					<LucideIcon name={categoryIcon} size={16} className="inline-block mr-1 text-gray-500" /> {categoryName}
 				</span>
 				<span className="inline-flex items-center px-2 py-0.5 rounded-full text-xs font-medium bg-purple-50 text-purple-700">
 					{candidateCount} {candidateCount === 1 ? "candidate" : "candidates"}