Add initial implementation of BOM management classes and data structure

- Created clsBOMManager for managing BOM data
- Added clsCategory and clsMaterialItem for category and material representation
- Implemented methods for loading and organizing BOM data from Excel
- Introduced .gitignore to exclude unnecessary files
- Added metadata JSON for module tracking

.gitignore

@@ -0,0 +1,16 @@
+__pycache__/
+.venv
+build
+dist
+log
+*.spec
+temp
+
+# Claude 临时文件
+.claude/
+tmpclaude-*
+*.log
+*workspace*
+*.png
+data/
+*.xlsm