fix(core): fix lint/type issues and small refactors

ts/cli/feature-handler.ts

@@ -1,4 +1,3 @@
-import process from 'node:process';
 import { execSync } from 'node:child_process';
 import { Nupst } from '../nupst.ts';
 import { logger } from '../logger.ts';

ts/cli/group-handler.ts

@@ -1,4 +1,3 @@
-import process from 'node:process';
 import { Nupst } from '../nupst.ts';
 import { type ITableColumn, logger } from '../logger.ts';
 import { theme } from '../colors.ts';

ts/cli/service-handler.ts

@@ -126,7 +126,7 @@ export class ServiceHandler {
   /**
    * Update NUPST from repository and refresh systemd service
    */
-  public async update(): Promise<void> {
+  public update(): void {
     try {
       // Check if running as root
       this.checkRootAccess(

ts/cli/ups-handler.ts

@@ -5,7 +5,7 @@ import { type ITableColumn, logger } from '../logger.ts';
 import { theme } from '../colors.ts';
 import * as helpers from '../helpers/index.ts';
 import type { ISnmpConfig, IUpsStatus as ISnmpUpsStatus, TUpsModel } from '../snmp/types.ts';
-import type { INupstConfig, IUpsConfig, IUpsStatus } from '../daemon.ts';
+import type { INupstConfig, IUpsConfig } from '../daemon.ts';
 import type { IActionConfig } from '../actions/base-action.ts';
 
 /**