refactor: replace CODE field source from column C to column I (66代码)

- Add COL_IDX_CODE66 constant for column I in M04_Config.bas
- Extend data reading range to include column I in M02_DataIO.ReadSourceData
- Use .Text property for column I to preserve leading zeros
- Update baseInfo array to use column I instead of column C in M01_Main.bas
- Set output code column to text format to prevent numeric conversion

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

VBA_BOMConverter/Modules/M01_Main.bas

@@ -95,8 +95,8 @@ Public Sub RunBOMConversion()
                     catData.Add strCat, New Collection
                 End If
 
-                ' 基础信息: 代号, 名称, 数量
-                baseInfo = Array(arrData(i, M04_Config.COL_IDX_CODE), _
+                ' 基础信息: 66代码, 名称, 数量（使用I列的66代码作为编码）
+                baseInfo = Array(arrData(i, M04_Config.COL_IDX_CODE66), _
                                  arrData(i, M04_Config.COL_IDX_NAME), _
                                  arrData(i, M04_Config.COL_IDX_QTY))