Add updateExisting option to furniture import

- Added updateExisting parameter to importSingleFurni and API routes
- When updateExisting=true, existing items are updated (catalog price/page) instead of failing
- Added catalogUpdated flag to ImportSingleResult
- Updates existing catalog entries (price, page) instead of skipping duplicates

src/types/furni.ts

@@ -93,6 +93,7 @@ export interface ImportSingleResult {
 	ok: boolean;
 	itemId?: number;
 	catalogItemId?: number | null;
+	catalogUpdated?: boolean;
 	dimensions?: { x: number; y: number; z: number };
 	spriteCount?: number;
 	warnings: string[];