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

VBA/vba_metadata.json

@@ -0,0 +1,65 @@
+{
+  "source_file": "C:\\Users\\Administrator\\Desktop\\新BOM\\AutoBOM\\YTHN-100.A0.532-BOM-1.2版 Claude.xlsm",
+  "modules": {
+    "ThisWorkbook.cls": {
+      "name": "ThisWorkbook",
+      "type": "DocumentModules",
+      "attributes": {},
+      "file": "DocumentModules\\ThisWorkbook.cls"
+    },
+    "Sheet3.cls": {
+      "name": "Sheet3",
+      "type": "DocumentModules",
+      "attributes": {},
+      "file": "DocumentModules\\Sheet3.cls"
+    },
+    "Sheet1.cls": {
+      "name": "Sheet1",
+      "type": "DocumentModules",
+      "attributes": {},
+      "file": "DocumentModules\\Sheet1.cls"
+    },
+    "Sheet2.cls": {
+      "name": "Sheet2",
+      "type": "DocumentModules",
+      "attributes": {},
+      "file": "DocumentModules\\Sheet2.cls"
+    },
+    "Sheet4.cls": {
+      "name": "Sheet4",
+      "type": "DocumentModules",
+      "attributes": {},
+      "file": "DocumentModules\\Sheet4.cls"
+    },
+    "clsCategory.cls": {
+      "name": "clsCategory",
+      "type": "ClassModules",
+      "attributes": {},
+      "file": "ClassModules\\clsCategory.cls"
+    },
+    "clsMaterialItem.cls": {
+      "name": "clsMaterialItem",
+      "type": "ClassModules",
+      "attributes": {},
+      "file": "ClassModules\\clsMaterialItem.cls"
+    },
+    "modBOMProcessor.bas": {
+      "name": "modBOMProcessor",
+      "type": "Modules",
+      "attributes": {},
+      "file": "Modules\\modBOMProcessor.bas"
+    },
+    "clsBOMManager.cls": {
+      "name": "clsBOMManager",
+      "type": "ClassModules",
+      "attributes": {},
+      "file": "ClassModules\\clsBOMManager.cls"
+    },
+    "Sheet6.cls": {
+      "name": "Sheet6",
+      "type": "DocumentModules",
+      "attributes": {},
+      "file": "DocumentModules\\Sheet6.cls"
+    }
+  }
+}