refactor(logger): optimize logging architecture with 6 improvements

1. Extract shared module: consolidate getLogDir() and isProduction()
   into shared.ts, eliminate duplication across logger modules
2. Make retention config effective: delay file transport creation
   until config is loaded, apply appRetention/auditRetention from config.yaml
3. Add before-quit log flush: close logger and audit logger on
   app exit to prevent log loss
4. Unify logError entry point: remove duplicate logError from index.ts,
   re-export from error-utils.ts with richer error context
5. Renderer log level filtering: add client-side level check in preload
   to skip IPC for filtered-out messages
6. Child logger cache + audit cleanup: cache child loggers in IPC
   handler for performance, remove redundant timestamp format in audit logger

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/main/ipc/settings-handler.ts

@@ -27,16 +27,13 @@ export function registerSettingsHandlers(): void {
   const erpConfigService = UserErpConfigService.getInstance()
 
   ipcMain.handle(IPC_CHANNELS.SETTINGS_GET_USER_TYPE, async (): Promise<IpcResult<UserType>> => {
-    return withErrorHandling(
-      async () => {
-        const userType = sessionManager.getUserType()
-        if (!userType) {
-          throw new ValidationError('未找到用户类型', 'VAL_INVALID_INPUT')
-        }
-        return userType as UserType
-      },
-      'settings:getUserType'
-    )
+    return withErrorHandling(async () => {
+      const userType = sessionManager.getUserType()
+      if (!userType) {
+        throw new ValidationError('未找到用户类型', 'VAL_INVALID_INPUT')
+      }
+      return userType as UserType
+    }, 'settings:getUserType')
   })
 
   ipcMain.handle(