style: configure deno fmt to use single quotes

- Add singleQuote: true to deno.json fmt configuration
- Reformat all files with single quotes using deno fmt

ts/cli/service-handler.ts

@@ -1,5 +1,5 @@
 import process from 'node:process';
-import { execSync } from "node:child_process";
+import { execSync } from 'node:child_process';
 import { Nupst } from '../nupst.ts';
 import { logger } from '../logger.ts';
 
@@ -129,7 +129,7 @@ export class ServiceHandler {
     try {
       // Check if running as root
       this.checkRootAccess(
-        'This command must be run as root to update NUPST and refresh the systemd service.'
+        'This command must be run as root to update NUPST and refresh the systemd service.',
       );
 
       const boxWidth = 45;
@@ -243,7 +243,7 @@ export class ServiceHandler {
 
       // Ask about removing configuration
       const removeConfig = await prompt(
-        'Do you want to remove the NUPST configuration files? (y/N): '
+        'Do you want to remove the NUPST configuration files? (y/N): ',
       );
 
       // Find the uninstall.sh script location
@@ -318,4 +318,4 @@ export class ServiceHandler {
 
     return { debugMode, cleanedArgs };
   }
-}
+}