feat(i18n): 공통/주요 화면 문자열 치환, 포맷 정책 적용, 언어 전환 UX 및 스캔 스크립트 추가

src/App.vue

@@ -7,8 +7,19 @@
       dark
     >
       <v-spacer />
-      <v-toolbar-title>보이스온 크리에이터 관리자</v-toolbar-title>
+      <v-toolbar-title>{{ $t('common.app.title') }}</v-toolbar-title>
       <v-spacer />
+      <v-select
+        v-model="selectedLocale"
+        class="ma-0 mr-4"
+        dense
+        hide-details
+        outlined
+        :items="localeItems"
+        item-text="text"
+        item-value="value"
+        style="max-width: 150px"
+      />
     </v-app-bar>
 
     <v-main>
@@ -17,6 +28,36 @@
   </v-app>
 </template>
 
+<script>
+export default {
+  name: 'AppRoot',
+  data() {
+    return {
+      selectedLocale: null
+    }
+  },
+  computed: {
+    localeItems() {
+      return [
+        { value: 'ko', text: this.$t('common.lang.ko') },
+        { value: 'en', text: this.$t('common.lang.en') },
+        { value: 'ja', text: this.$t('common.lang.ja') }
+      ]
+    }
+  },
+  watch: {
+    selectedLocale(v) {
+      if (!v) return
+      this.$i18n.locale = v
+      try { localStorage.setItem('locale', v) } catch (e) { /* ignore */ }
+    }
+  },
+  created() {
+    this.selectedLocale = this.$i18n && this.$i18n.locale ? this.$i18n.locale : 'ko'
+  }
+}
+</script>
+
 <style lang="scss">
 #app {
   font-family: Avenir, Helvetica, Arial, sans-serif;