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

src/main/ipc/file-handler.ts

@@ -0,0 +1,55 @@
+import { ipcMain } from 'electron'
+import * as fs from 'fs/promises'
+import * as path from 'path'
+
+/**
+ * Register IPC handlers for file operations
+ */
+export function registerFileHandlers(): void {
+  // Read file content
+  ipcMain.handle('file:read', async (_event, filePath: string): Promise<string> => {
+    try {
+      return await fs.readFile(filePath, 'utf-8')
+    } catch (error) {
+      const message = error instanceof Error ? error.message : 'Failed to read file'
+      throw new Error(message)
+    }
+  })
+
+  // Write content to file
+  ipcMain.handle('file:write', async (_event, filePath: string, content: string): Promise<void> => {
+    try {
+      // Ensure directory exists
+      const dir = path.dirname(filePath)
+      await fs.mkdir(dir, { recursive: true })
+      await fs.writeFile(filePath, content, 'utf-8')
+    } catch (error) {
+      const message = error instanceof Error ? error.message : 'Failed to write file'
+      throw new Error(message)
+    }
+  })
+
+  // Check if file exists
+  ipcMain.handle('file:exists', async (_event, filePath: string): Promise<boolean> => {
+    try {
+      await fs.access(filePath)
+      return true
+    } catch {
+      return false
+    }
+  })
+
+  // List files in directory
+  ipcMain.handle('file:list', async (_event, dirPath: string): Promise<string[]> => {
+    try {
+      const entries = await fs.readdir(dirPath, { withFileTypes: true })
+      return entries
+        .filter((entry) => entry.isFile())
+        .map((entry) => entry.name)
+        .sort()
+    } catch (error) {
+      const message = error instanceof Error ? error.message : 'Failed to list directory'
+      throw new Error(message)
+    }
+  })
+}