refactor(web): migrate to TypeScript + standard Vue3 structure

memora-web/src/views/Statistics.vue

@@ -18,11 +18,18 @@
   </div>
 </template>
 
-<script setup>
+<script setup lang="ts">
 import { onMounted, ref } from 'vue'
 import { getStatistics } from '../services/api'
 
-const stats = ref({})
+import type { Stats } from '../services/api'
+
+const stats = ref<Stats>({
+  total_words: 0,
+  mastered_words: 0,
+  need_review: 0,
+  today_reviewed: 0
+})
 async function refresh() {
   const res = await getStatistics()
   stats.value = res.data ?? res