refactor: simplify useLocalStorage (remove APP_PREFIX) and finalize QR Code tool

src/composables/useLocalStorage.js

@@ -1,16 +1,20 @@
 import { ref, watch } from 'vue'
 
-export function useLocalStorage(key, defaultValue) {
+export function useLocalStorage(key, defaultValue, toolPrefix = '') {
+  // Construct prefixed key: [toolPrefix-]key
+  const prefixPart = toolPrefix ? `${toolPrefix}-` : ''
+  const prefixedKey = `${prefixPart}${key}`
+
   // Initialize state from local storage or default value
-  const storedValue = localStorage.getItem(key)
+  const storedValue = localStorage.getItem(prefixedKey)
   const data = ref(storedValue ? JSON.parse(storedValue) : defaultValue)
 
   // Watch for changes and update local storage
   watch(data, (newValue) => {
     if (newValue === null || newValue === undefined) {
-      localStorage.removeItem(key)
+      localStorage.removeItem(prefixedKey)
     } else {
-      localStorage.setItem(key, JSON.stringify(newValue))
+      localStorage.setItem(prefixedKey, JSON.stringify(newValue))
     }
   }, { deep: true })