feat: implement settings interface with user permission control

New Features:
- Add SettingsPage component with Admin/User view differentiation
- Create ConfigManager service for .env file management
- Add IPC handlers for settings CRUD operations
- Implement connection testing for ERP and database
- Add settings navigation to main app

Files Created:
- src/main/types/settings.types.ts - Type definitions
- src/main/services/config/config-manager.ts - Config service
- src/main/ipc/settings-handler.ts - IPC handlers
- src/renderer/src/pages/SettingsPage.tsx - React UI component

Files Modified:
- src/main/ipc/index.ts - Register settings handlers
- src/preload/index.ts - Expose settings API
- src/preload/index.d.ts - Add SettingsAPI type
- src/renderer/src/App.tsx - Add settings navigation

Co-Authored-By: Claude (qwen3.5-plus) <noreply@anthropic.com>

src/main/ipc/index.ts

@@ -10,6 +10,7 @@ import { registerDatabaseHandlers } from './database-handler'
 import { registerResolverHandlers } from './resolver-handler'
 import { registerAuthHandlers } from './auth-handler'
 import { registerValidationHandlers } from './validation-handler'
+import { registerSettingsHandlers } from './settings-handler'
 
 /**
  * Register all IPC handlers
@@ -22,4 +23,5 @@ export function registerIpcHandlers(): void {
   registerResolverHandlers()
   registerAuthHandlers()
   registerValidationHandlers()
+  registerSettingsHandlers()
 }