feat: Implement supplier export functionality with workbook generation

- Add `writeSupplierWorkbook` function to create Excel workbooks for supplier analysis results.
- Introduce `SupplierExportSummary` type for summarizing export data.
- Create tests for `writeSupplierWorkbook` to ensure correct sheet creation and data population.
- Implement supplier scoring logic in `supplier-scoring.ts` to evaluate product profitability and demand.
- Add tests for supplier scoring to validate scoring logic and verdict determination.
- Enhance UPC file analysis to integrate supplier scoring and export results to Excel.
- Update database writing logic to accommodate new supplier analysis results.
- Refactor types to include supplier-specific data structures and scoring metrics.
- Ensure proper cleanup of temporary files after tests.

src/bestsellers-by-category.ts

@@ -1192,7 +1192,7 @@ export async function main(): Promise<void> {
 
   mkdirSync(args.outputDir, { recursive: true });
   const DB_PATH =
-    process.env.RESULTS_DB_PATH || path.join(process.cwd(), "results.db");
+    process.env.RESULTS_DB_PATH || path.join(process.cwd(), "db", "results.db");
   initDb(DB_PATH);
   const db = getDb(DB_PATH);