feat: implement Excel parser service

Implement Excel parsing module for ERP exported files following TDD principles.

Key features:
- Parse Excel files with multiple orders per file
- Extract order header information (production order, product code, etc.)
- Extract material data rows with 13 fields
- Handle empty orders gracefully
- Detect footer rows (制单人/打印人)
- Map Chinese field names to English property names
- Support field name mapping from Python reference

Implementation:
- ExcelParser class with parse() method
- DiscreteMaterialPlan and ExcelParseOptions types
- OrderHeader interface for order metadata
- Test fixtures with realistic Excel structure
- Comprehensive unit tests (3 tests, all passing)

Reference: playwrite/utils/excel_converter.py

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

tests/unit/excel-parser.test.ts

@@ -0,0 +1,59 @@
+import { describe, it, expect } from 'vitest';
+import { ExcelParser } from '../../src/main/services/excel/excel-parser';
+import type { DiscreteMaterialPlan } from '../../src/main/types/excel.types';
+import path from 'path';
+
+describe('Excel Parser', () => {
+  it('should parse Excel file and extract material plans', async () => {
+    const parser = new ExcelParser();
+    const filePath = path.resolve(__dirname, '../fixtures/test-export.xlsx');
+
+    const plans = await parser.parse(filePath);
+
+    expect(Array.isArray(plans)).toBe(true);
+    expect(plans.length).toBeGreaterThan(0);
+
+    const firstPlan = plans[0];
+    expect(firstPlan).toHaveProperty('orderNumber');
+    expect(firstPlan).toHaveProperty('materialCode');
+  });
+
+  it('should parse all material fields correctly', async () => {
+    const parser = new ExcelParser();
+    const filePath = path.resolve(__dirname, '../fixtures/test-export.xlsx');
+
+    const plans = await parser.parse(filePath);
+
+    expect(plans.length).toBe(3);
+
+    // Check first material
+    expect(plans[0].orderNumber).toBe('SC202501001');
+    expect(plans[0].materialCode).toBe('M001');
+    expect(plans[0].materialName).toBe('钢材A');
+    expect(plans[0].specification).toBe('规格1');
+    expect(plans[0].model).toBe('型号1');
+    expect(plans[0].drawingNumber).toBe('图号1');
+    expect(plans[0].material).toBe('材质1');
+    expect(plans[0].quantity).toBe(50);
+    expect(plans[0].unit).toBe('kg');
+    expect(plans[0].requiredDate).toBe('2025-02-10');
+    expect(plans[0].warehouse).toBe('仓库1');
+    expect(plans[0].unitUsage).toBe(0.5);
+    expect(plans[0].cumulativeOutboundQty).toBe(0);
+
+    // Check third material (with some empty fields)
+    expect(plans[2].materialCode).toBe('M003');
+    expect(plans[2].materialName).toBe('配件C');
+    expect(plans[2].quantity).toBe(200);
+  });
+
+  it('should handle empty orders gracefully', async () => {
+    const parser = new ExcelParser();
+    const filePath = path.resolve(__dirname, '../fixtures/test-empty-orders.xlsx');
+
+    const plans = await parser.parse(filePath);
+
+    expect(plans).toBeDefined();
+    expect(plans.length).toBe(0);
+  });
+});