feat: implement IPC handlers, database services and Extractor UI

- Add SqlServerService and MySqlService for database persistence
- Implement IPC handlers for file, extractor, cleaner, and database operations
- Define IPC API types and update preload script
- Create ExtractorPage UI with OrderNumberInput component
- Add unit and integration tests for MySQL and SQL Server
- Update vitest config with path aliases

tests/unit/sql-server.test.ts

@@ -0,0 +1,73 @@
+/**
+ * Unit tests for SqlServerService
+ * These tests do not require a SQL Server instance
+ */
+
+import { describe, it, expect, beforeEach } from 'vitest'
+import { SqlServerService } from '@main/services/database/sql-server'
+
+const mockConfig = {
+  server: 'localhost',
+  port: 1433,
+  user: 'test',
+  password: 'test',
+  database: 'testdb',
+  options: {
+    encrypt: false,
+    trustServerCertificate: true
+  }
+}
+
+describe('SqlServerService Unit Tests', () => {
+  let service: SqlServerService
+
+  beforeEach(() => {
+    service = new SqlServerService(mockConfig)
+  })
+
+  describe('constructor', () => {
+    it('should create service with config', () => {
+      expect(service).toBeDefined()
+      expect(service.isConnected()).toBe(false)
+    })
+  })
+
+  describe('isConnected', () => {
+    it('should return false when not connected', () => {
+      expect(service.isConnected()).toBe(false)
+    })
+  })
+
+  describe('connect', () => {
+    it('should throw error with invalid credentials', async () => {
+      // This tests error handling without needing a real server
+      const invalidConfig = {
+        ...mockConfig,
+        server: 'invalid-host-that-does-not-exist'
+      }
+      const invalidService = new SqlServerService(invalidConfig)
+
+      await expect(invalidService.connect()).rejects.toThrow('Failed to connect to SQL Server')
+    })
+  })
+
+  describe('query', () => {
+    it('should throw error when not connected', async () => {
+      await expect(service.query('SELECT 1')).rejects.toThrow('Not connected to SQL Server')
+    })
+  })
+
+  describe('transaction', () => {
+    it('should throw error when not connected', async () => {
+      await expect(service.transaction([{ sql: 'SELECT 1' }])).rejects.toThrow(
+        'Not connected to SQL Server'
+      )
+    })
+  })
+
+  describe('disconnect', () => {
+    it('should resolve when not connected', async () => {
+      await expect(service.disconnect()).resolves.not.toThrow()
+    })
+  })
+})