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/CandidateCard.tsx

@@ -1,4 +1,5 @@
 import { formatPrice, formatWeight } from "../lib/formatters";
+import { LucideIcon } from "../lib/iconData";
 import { useUIStore } from "../stores/uiStore";
 
 interface CandidateCardProps {
@@ -7,7 +8,7 @@ interface CandidateCardProps {
 	weightGrams: number | null;
 	priceCents: number | null;
 	categoryName: string;
-	categoryEmoji: string;
+	categoryIcon: string;
 	imageFilename: string | null;
 	threadId: number;
 	isActive: boolean;
@@ -19,7 +20,7 @@ export function CandidateCard({
 	weightGrams,
 	priceCents,
 	categoryName,
-	categoryEmoji,
+	categoryIcon,
 	imageFilename,
 	threadId,
 	isActive,
@@ -41,7 +42,7 @@ export function CandidateCard({
 					/>
 				) : (
 					<div className="w-full h-full flex flex-col items-center justify-center">
-						<span className="text-3xl">{categoryEmoji}</span>
+						<LucideIcon name={categoryIcon} size={36} className="text-gray-400" />
 					</div>
 				)}
 			</div>
@@ -61,7 +62,7 @@ export function CandidateCard({
 						</span>
 					)}
 					<span className="inline-flex items-center px-2 py-0.5 rounded-full text-xs font-medium bg-gray-50 text-gray-600">
-						{categoryEmoji} {categoryName}
+						<LucideIcon name={categoryIcon} size={14} className="inline-block mr-1 text-gray-500" /> {categoryName}
 					</span>
 				</div>
 				<div className="flex gap-2">