feat: migrate ERP configuration from .env to per-user database storage

- Moved ERP credentials (URL, username, password) from environment variables to dbo_BIPUsers table
- Each user now has their own ERP configuration stored in the database
- Added UserErpConfigService for managing per-user ERP settings
- Updated cleaner and extractor handlers to fetch ERP config from database instead of .env
- Removed ERP fields from ConfigManager UI editable fields
- Added new IPC handlers and preload APIs for user ERP config management
- Includes migration script to transfer existing .env ERP settings to database
- Added migration guide documentation

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

src/main/ipc/index.ts

@@ -12,6 +12,7 @@ import { registerAuthHandlers } from './auth-handler'
 import { registerValidationHandlers } from './validation-handler'
 import { registerSettingsHandlers } from './settings-handler'
 import { registerMaterialTypeHandlers } from './material-type-handler'
+import { registerUserErpConfigHandlers } from './user-erp-config-handler'
 import { createLogger } from '../services/logger'
 import { getErrorMessage, getErrorCode, isBaseError } from '../types/errors'
 
@@ -75,5 +76,6 @@ export function registerIpcHandlers(): void {
   registerValidationHandlers()
   registerSettingsHandlers()
   registerMaterialTypeHandlers()
+  registerUserErpConfigHandlers()
   log.info('All IPC handlers registered')
 }