feat(lastleg): add direct inventory balance detail

lastleg-service/src/main/java/com/baiyue/lastleg/inventory/query/controller/InventoryQueryController.java

@@ -56,6 +56,16 @@ public class InventoryQueryController {
         return ApiResponse.success(service.balances(platformScope(user, customerId), query));
     }
 
+    @GetMapping(BASE_PATH + "/balances/{balanceId}")
+    @PreAuthorize("hasAuthority('" + OverseasPermissions.INVENTORY_LIST + "')")
+    @Operation(summary = "Get one inventory balance", description = "Returns one non-zero inventory balance by ID and optional customer scope. Required authority: " + OverseasPermissions.INVENTORY_LIST)
+    public ApiResponse<InventoryBalanceView> balance(
+        @AuthenticationPrincipal AuthenticatedUser user,
+        @PathVariable long balanceId,
+        @RequestParam(required = false) String customerId) {
+        return ApiResponse.success(service.balance(platformScope(user, customerId), balanceId));
+    }
+
     @GetMapping(BASE_PATH + "/balances/{balanceId}/positions")
     @PreAuthorize("hasAuthority('" + OverseasPermissions.INVENTORY_LIST + "')")
     @Operation(summary = "List pallet and batch positions for one inbound-order balance", description = "Required authority: " + OverseasPermissions.INVENTORY_LIST)

lastleg-service/src/main/java/com/baiyue/lastleg/inventory/query/mapper/InventoryQueryMapper.java

@@ -111,6 +111,17 @@ public interface InventoryQueryMapper {
     @Select("SELECT * FROM ll_inventory_balance WHERE id=#{balanceId} LIMIT 1")
     InventoryBalance findBalance(@Param("balanceId") long balanceId);
 
+    @Select("SELECT * FROM ll_inventory_balance WHERE customer_id=#{customerId} AND id=#{balanceId} " +
+        "AND (available_packages+hold_packages+allocated_packages+picked_packages+in_transit_packages+" +
+        "receiving_packages+procurement_packages)>0 LIMIT 1")
+    InventoryBalance ownedVisibleBalance(@Param("customerId") String customerId,
+                                          @Param("balanceId") long balanceId);
+
+    @Select("SELECT * FROM ll_inventory_balance WHERE id=#{balanceId} " +
+        "AND (available_packages+hold_packages+allocated_packages+picked_packages+in_transit_packages+" +
+        "receiving_packages+procurement_packages)>0 LIMIT 1")
+    InventoryBalance visibleBalance(@Param("balanceId") long balanceId);
+
     String LEDGER_FILTER = " WHERE 1=1" +
         "<if test='customerId != null and customerId != \"\"'> AND customer_id=#{customerId}</if>" +
         "<if test='q.overseasWarehouseId != null and q.overseasWarehouseId != \"\"'> AND overseas_warehouse_id=#{q.overseasWarehouseId}</if>" +

lastleg-service/src/main/java/com/baiyue/lastleg/inventory/query/service/InventoryQueryService.java

@@ -57,6 +57,16 @@ public class InventoryQueryService {
         return page(records, query.page(), query.size(), total);
     }
 
+    public InventoryBalanceView balance(String customerId, long balanceId) {
+        InventoryBalance balance = customerId == null
+            ? mapper.visibleBalance(balanceId)
+            : mapper.ownedVisibleBalance(customerId, balanceId);
+        if (balance == null) {
+            throw new ResponseStatusException(HttpStatus.NOT_FOUND, "Inventory balance not found");
+        }
+        return balanceView(balance);
+    }
+
     public List<InventoryPositionView> positions(String customerId, long balanceId,
                                                  InventoryQueryRequests.PositionQuery query) {
         validateStatus(query.inventoryStatus(), POSITION_STATUSES);