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/fixtures/create-fixtures.ts

@@ -0,0 +1,156 @@
+import ExcelJS from 'exceljs';
+import path from 'path';
+
+/**
+ * Create test fixture Excel files for unit tests
+ */
+
+async function createTestFixture() {
+  const workbook = new ExcelJS.Workbook();
+  const worksheet = workbook.addWorksheet('Sheet1');
+
+  // Row 1: Order title
+  worksheet.addRow([null, '离散备料计划']);
+
+  // Row 2-5: Order header info
+  worksheet.addRow([null, '生产部门：', null, '生产车间', '产品编码：', null, 'P001']);
+  worksheet.addRow([null, '生产订单：', null, 'SC202501001', '产品名称：', null, '测试产品A']);
+  worksheet.addRow([null, '产品规格：', null, '标准规格', '计划数量：', null, '100']);
+  worksheet.addRow([null, '单位：', null, '件', '需用日期：', null, '2025-02-15']);
+
+  // Row 6: Empty row before table header
+  worksheet.addRow([]);
+
+  // Row 7: Table header
+  worksheet.addRow([
+    null,
+    '序号',
+    '材料编码',
+    '材料名称',
+    '规格',
+    '型号',
+    '图号',
+    '物料材质',
+    '计划数量',
+    '单位',
+    '需用日期',
+    '发料仓库',
+    '单位用量',
+    '累计出库数量',
+  ]);
+
+  // Row 8-10: Material data
+  worksheet.addRow([
+    null,
+    1,
+    'M001',
+    '钢材A',
+    '规格1',
+    '型号1',
+    '图号1',
+    '材质1',
+    50,
+    'kg',
+    '2025-02-10',
+    '仓库1',
+    0.5,
+    0,
+  ]);
+  worksheet.addRow([
+    null,
+    2,
+    'M002',
+    '塑料B',
+    '规格2',
+    '型号2',
+    '图号2',
+    '材质2',
+    100,
+    'kg',
+    '2025-02-12',
+    '仓库1',
+    1.0,
+    20,
+  ]);
+  worksheet.addRow([
+    null,
+    3,
+    'M003',
+    '配件C',
+    '规格3',
+    null,
+    null,
+    null,
+    200,
+    '件',
+    '2025-02-14',
+    '仓库2',
+    2.0,
+    50,
+  ]);
+
+  // Row 11: Footer info
+  worksheet.addRow([null, '制单人：', null, '张三', '打印人：', null, '李四']);
+  worksheet.addRow([null, '打印日期：', null, '2025-01-15']);
+
+  // Save file
+  const filePath = path.resolve(__dirname, 'test-export.xlsx');
+  await workbook.xlsx.writeFile(filePath);
+  console.log('Created test fixture:', filePath);
+}
+
+async function createEmptyOrdersFixture() {
+  const workbook = new ExcelJS.Workbook();
+  const worksheet = workbook.addWorksheet('Sheet1');
+
+  // Row 1: Order title
+  worksheet.addRow([null, '离散备料计划']);
+
+  // Row 2-5: Order header info
+  worksheet.addRow([null, '生产部门：', null, '生产车间', '产品编码：', null, 'P002']);
+  worksheet.addRow([null, '生产订单：', null, 'SC202501002', '产品名称：', null, '测试产品B']);
+  worksheet.addRow([null, '产品规格：', null, '特殊规格', '计划数量：', null, '50']);
+  worksheet.addRow([null, '单位：', null, '套', '需用日期：', null, '2025-03-01']);
+
+  // Row 6: Empty row before table header
+  worksheet.addRow([]);
+
+  // Row 7: Table header
+  worksheet.addRow([
+    null,
+    '序号',
+    '材料编码',
+    '材料名称',
+    '规格',
+    '型号',
+    '图号',
+    '物料材质',
+    '计划数量',
+    '单位',
+    '需用日期',
+    '发料仓库',
+    '单位用量',
+    '累计出库数量',
+  ]);
+
+  // Row 8: Empty row (no data)
+  worksheet.addRow([]);
+
+  // Row 9: Footer info
+  worksheet.addRow([null, '制单人：', null, '王五', '打印人：', null, '赵六']);
+  worksheet.addRow([null, '打印日期：', null, '2025-01-16']);
+
+  // Save file
+  const filePath = path.resolve(__dirname, 'test-empty-orders.xlsx');
+  await workbook.xlsx.writeFile(filePath);
+  console.log('Created empty orders fixture:', filePath);
+}
+
+async function main() {
+  console.log('Creating test fixture Excel files...');
+  await createTestFixture();
+  await createEmptyOrdersFixture();
+  console.log('Done!');
+}
+
+main().catch(console.error);