feat: Enhance Stock Ledger functionality with item details and filters

- Updated StockService to compute running balance on read and include item SKU, name, category, and brand in StockLedgerRowDto.
- Modified GetLedgerAsync method to accept categoryId and brandId parameters for filtering.
- Enhanced StockController to support new query parameters for ledger retrieval.
- Updated StockDtos to include additional item information in StockLedgerRowDto.
- Adjusted frontend Stock Ledger page to display item details and implement searchable item picker.
- Added tests for StockLedger to verify running balance calculations and filtering by category and brand.
- Updated appsettings for service URLs and modified login page navigation logic.

Frontend/erp-system/lib/api/stock.ts

@@ -7,6 +7,9 @@ export interface LedgerQuery {
   itemId?: number
   warehouseId?: number
   branchId?: number
+  /** Only items in this category / of this brand. */
+  categoryId?: number
+  brandId?: number
   /** `YYYY-MM-DD`. */
   from?: string
   to?: string