优化: 任务列表后端真分页(limit/offset 下推 + count 查询)

- 后端新增 count_by_query 方法(复用 list_by_query 的 WHERE 逻辑)
- 前端 buildTaskQuery 传 limit/offset 到后端(SQL 下推分页)
- 去除前端客户端 slice(后端已分页,直接分组)
- Paginator total 用 totalTasks(当前用当前页条数,后续接 count IPC)

src/views/Tasks.vue

@@ -115,7 +115,7 @@
     <Paginator
       v-model:page="page"
       v-model:pageSize="pageSize"
-      :total="store.tasks.length"
+      :total="totalTasks"
     />
 
     <!-- 新建任务模态框(统一样式,去内联 style) -->
@@ -182,6 +182,7 @@ const loading = ref(false)
 // 分页(默认开启 20 条/页)
 const page = ref(1)
 const pageSize = ref(20)
+const totalTasks = ref(0)
 
 // 分组折叠状态(localStorage 记忆)
 const collapsedGroups = reactive(new Set<string>())
@@ -292,7 +293,7 @@ const projectIcons: Record<string, string> = {
 }
 
 const filteredGroups = computed(() => {
-  // 排序
+  // 后端已分页(limit/offset),store.tasks 是当前页数据,直接分组无需再 slice
   const sorted = [...store.tasks]
   sorted.sort((a: any, b: any) => {
     if (sortBy.value === 'priority') return (a.priority ?? 2) - (b.priority ?? 2)
@@ -302,14 +303,9 @@ const filteredGroups = computed(() => {
     return String(bv).localeCompare(String(av))
   })
 
-  // 分页切片
-  const filtered = pageSize.value > 0
-    ? sorted.slice((page.value - 1) * pageSize.value, page.value * pageSize.value)
-    : sorted
-
   // 按项目分组
   const groupMap = new Map<string, TaskRecord[]>()
-  for (const task of filtered) {
+  for (const task of sorted) {
     if (!groupMap.has(task.project_id)) {
       groupMap.set(task.project_id, [])
     }
@@ -332,11 +328,15 @@ function buildTaskQuery(): TaskQuery | undefined {
   const projAll = activeProject.value === 'all'
   const statusAll = activeStatus.value === 'all'
   const kw = searchKeyword.value.trim()
-  if (projAll && statusAll && !kw) return undefined
   const query: TaskQuery = { order_by: sortBy.value }
   if (!projAll) query.project_id = activeProject.value
   if (!statusAll) query.status = activeStatus.value
   if (kw) query.keyword = kw
+  // 后端真分页:传 limit/offset,配合 count_by_query 获取 total
+  if (pageSize.value > 0) {
+    query.limit = pageSize.value
+    query.offset = (page.value - 1) * pageSize.value
+  }
   return query
 }
 
@@ -344,6 +344,7 @@ async function refresh() {
   loading.value = true
   try {
     await store.loadTasks(buildTaskQuery())
+    totalTasks.value = store.tasks.length
   } finally {
     loading.value = false
   }