fix: 第21轮搜索审计修复 — OR模式NOT回退/子组虚条目/日期OR模式等10项

Bug-R21-1 (CRITICAL): OR模式NOT分离过度 — A OR NOT B语义错误，恢复or_(*conditions)
Bug-R21-2 (CRITICAL): 双重嵌套括号sub_group_refs虚条目 — 仅当_ungrouped非空时写入
Bug-R21-3 (HIGH): negated_date_ranges被覆盖 — =改为|=
Bug-R21-4 (MEDIUM): 日期/PMID/DOI/PMC条件在OR模式始终AND — 合并为or_(*conditions)
Bug-R21-5 (MEDIUM): _parse_atom无条件消费任何词符 — 类型验证守卫
Bug-R21-6 (MEDIUM): 模态框双重goToPage(1) — 按钮只关弹窗，搜索由watcher触发
Bug-R21-7 (MEDIUM): page.value失败后不回退 — 捕获异常恢复前一页
Bug-R21-8 (LOW): 空引号""[TI]产生空Term — text为空时跳过
Bug-R21-9 (LOW): 冗余函数内import re — 使用模块级导入

frontend/src/composables/usePagination.ts

@@ -21,8 +21,13 @@ export function usePagination(opts: UsePaginationOptions) {
   const hasMore = computed(() => page.value < totalPages.value)
 
   async function goToPage(n: number) {
+    const prev = page.value
     page.value = n
-    await fetchFn(n)
+    try {
+      await fetchFn(n)
+    } catch {
+      page.value = prev
+    }
   }
 
   return { page, pageSize, total, totalPages, hasMore, goToPage }

frontend/src/views/app/SearchView.vue

@@ -958,7 +958,7 @@ const specialTags = computed(() => filterOptions.value?.special_tags || {})
     <template #footer>
       <div style="display:flex;justify-content:space-between;align-items:center">
         <span style="font-size:13px;color:var(--text-muted)">已选择 {{ pubTypes.length }} 项</span>
-        <NButton size="small" type="primary" @click="showPubTypeModal = false; goToPage(1)">确定</NButton>
+        <NButton size="small" type="primary" @click="showPubTypeModal = false">确定</NButton>
       </div>
     </template>
   </NModal>
@@ -978,7 +978,7 @@ const specialTags = computed(() => filterOptions.value?.special_tags || {})
     </div>
     <template #footer>
       <div style="display:flex;justify-content:flex-end">
-        <NButton size="small" type="primary" @click="showLangModal = false; goToPage(1)">确定</NButton>
+        <NButton size="small" type="primary" @click="showLangModal = false">确定</NButton>
       </div>
     </template>
   </NModal>
@@ -994,7 +994,7 @@ const specialTags = computed(() => filterOptions.value?.special_tags || {})
     </div>
     <template #footer>
       <div style="display:flex;justify-content:flex-end">
-        <NButton size="small" type="primary" @click="showAgeModal = false; goToPage(1)">确定</NButton>
+        <NButton size="small" type="primary" @click="showAgeModal = false">确定</NButton>
       </div>
     </template>
   </NModal>