feat(06-02): replace EmojiPicker with IconPicker across all category components

- CategoryPicker shows LucideIcon prefix and uses IconPicker for inline create
- CategoryHeader displays LucideIcon in view mode and IconPicker in edit mode
- OnboardingWizard uses IconPicker for category creation step
- CreateThreadModal drops emoji from category select options
- Fixed categoryEmoji -> categoryIcon in routes and useCategories hook

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

src/client/routes/setups/$setupId.tsx

@@ -66,7 +66,7 @@ function SetupDetailPage() {
     {
       items: typeof setup.items;
       categoryName: string;
-      categoryEmoji: string;
+      categoryIcon: string;
     }
   >();
 
@@ -78,7 +78,7 @@ function SetupDetailPage() {
       groupedItems.set(item.categoryId, {
         items: [item],
         categoryName: item.categoryName,
-        categoryEmoji: item.categoryEmoji,
+        categoryIcon: item.categoryIcon,
       });
     }
   }
@@ -177,7 +177,7 @@ function SetupDetailPage() {
           {Array.from(groupedItems.entries()).map(
             ([
               categoryId,
-              { items: categoryItems, categoryName, categoryEmoji },
+              { items: categoryItems, categoryName, categoryIcon },
             ]) => {
               const catWeight = categoryItems.reduce(
                 (sum, item) => sum + (item.weightGrams ?? 0),
@@ -192,7 +192,7 @@ function SetupDetailPage() {
                   <CategoryHeader
                     categoryId={categoryId}
                     name={categoryName}
-                    emoji={categoryEmoji}
+                    icon={categoryIcon}
                     totalWeight={catWeight}
                     totalCost={catCost}
                     itemCount={categoryItems.length}
@@ -206,7 +206,7 @@ function SetupDetailPage() {
                         weightGrams={item.weightGrams}
                         priceCents={item.priceCents}
                         categoryName={categoryName}
-                        categoryEmoji={categoryEmoji}
+                        categoryIcon={categoryIcon}
                         imageFilename={item.imageFilename}
                         onRemove={() => removeItem.mutate(item.id)}
                       />