style: standardize VBA property and method name casing

Standardize all VBA property and method names to lowercase for consistent code style:
- Err object: Err.Description → err.Description, Err.Number → err.Number
- Collection properties: .Count → .count
- Range properties: .Rows.Count → .Rows.count, .Row → .row
- Dictionary methods: .Keys → .keys, .Exists → .exists
- Worksheet properties: .Sheets.Count → .Sheets.count
- Fix typo: Thisworkbook.Path → ThisWorkbook.Path

VBA is case-insensitive, but consistent lowercase convention improves readability.

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

VBA_BOMConverter/Modules/M01_Main.bas

@@ -126,7 +126,7 @@ ExitHandler:
     Exit Sub
 
 MainErrorHandler:
-    MsgBox "发生运行时错误: " & Err.Description, vbCritical
+    MsgBox "发生运行时错误: " & err.Description, vbCritical
     Resume ExitHandler
 End Sub
 
@@ -304,7 +304,7 @@ Public Sub GeneratePreprocessingReport()
 ReportErrorHandler:
     Application.StatusBar = False
     MsgBox "生成报表时出错：" & vbCrLf & _
-           "错误 " & Err.Number & ": " & Err.Description, _
+           "错误 " & err.Number & ": " & err.Description, _
            vbCritical, "报表生成错误"
 
 ReportExitHandler: