feat(task-logs): 实现任务日志 SSE 实时推送

实现任务日志 SSE 实时推送功能，解决前端无法流式输出日志的问题

变更内容：
- 后端：新增 /task-logs/stream SSE 端点，支持实时日志推送
- 后端：实现 2 秒轮询间隔检测新日志，支持心跳机制
- 后端：支持通过 query 参数 access_token 传递 JWT 认证
- 前端：新增 createTaskLogStream 函数封装 EventSource
- 前端：修改 TaskCenter.vue 集成 SSE，支持实时更新和自动滚动
- 前端：添加流式连接状态指示器

关联 commit：
- 实现后端 SSE Stream 方法
- 注册 SSE 路由
- 实现前端 SSE 客户端
- 集成 SSE 到任务中心页面

frontend/src/api/taskLog.ts

@@ -79,3 +79,49 @@ function parseResponseBody(text: string) {
     return { error: text }
   }
 }
+
+export interface TaskLogStreamCallbacks {
+  onInit?: (lines: TaskLogLine[]) => void
+  onUpdate?: (lines: TaskLogLine[]) => void
+  onFinished?: () => void
+  onError?: (error: string) => void
+}
+
+export function createTaskLogStream(taskId: string, callbacks: TaskLogStreamCallbacks): EventSource {
+  const token = getToken()
+  const url = `/auth/api/v1/task-logs/stream?task_id=${encodeURIComponent(taskId)}&access_token=${encodeURIComponent(token || '')}`
+
+  const es = new EventSource(url)
+
+  es.onmessage = (event) => {
+    try {
+      const data = JSON.parse(event.data)
+      switch (data.type) {
+        case 'init':
+          callbacks.onInit?.(Array.isArray(data.lines) ? data.lines : [])
+          break
+        case 'update':
+          callbacks.onUpdate?.(Array.isArray(data.lines) ? data.lines : [])
+          break
+        case 'finished':
+          callbacks.onFinished?.()
+          es.close()
+          break
+        case 'error':
+          callbacks.onError?.(data.error || 'Unknown error')
+          break
+      }
+    } catch {
+      // ignore parse errors for heartbeat etc.
+    }
+  }
+
+  es.onerror = () => {
+    // EventSource will auto-reconnect, but we report connection errors
+    if (es.readyState === EventSource.CLOSED) {
+      callbacks.onError?.('Connection closed')
+    }
+  }
+
+  return es
+}

frontend/src/views/task/TaskCenter.vue

@@ -52,6 +52,7 @@
           <h3>
             <span>任务日志</span>
             <span class="selected-name">{{ selectedTaskName }}</span>
+            <span v-if="isStreaming" class="streaming-indicator">● 实时更新中</span>
           </h3>
           <span class="meta">{{ selectedTaskMeta }}</span>
         </div>
@@ -72,8 +73,8 @@
 </template>
 
 <script setup lang="ts">
-import { computed, onMounted, ref, watch } from 'vue'
-import { taskLogApi, type TaskLogLine, type TaskLogSummary } from '@/api/taskLog'
+import { computed, onMounted, onUnmounted, ref, watch } from 'vue'
+import { taskLogApi, createTaskLogStream, type TaskLogLine, type TaskLogSummary } from '@/api/taskLog'
 import { useBusinessLineStore } from '@/stores/businessLine'
 import { useBusinessLineMockProfile } from '@/utils/businessLineMock'
 
@@ -87,6 +88,8 @@ const logs = ref<TaskLogLine[]>([])
 const loadingTasks = ref(false)
 const loadingLogs = ref(false)
 const lastLoadedAt = ref<Date | null>(null)
+const isStreaming = ref(false)
+let eventSource: EventSource | null = null
 
 const selectedTask = computed(() => tasks.value.find((task) => task.id === selectedTaskId.value))
 const selectedTaskName = computed(() => selectedTask.value?.name || '未选择')
@@ -122,6 +125,8 @@ async function loadLogs(taskId: string) {
     const data = await taskLogApi.get(taskId)
     logs.value = data.lines
     lastLoadedAt.value = new Date()
+    // 启动 SSE 流式更新
+    startStream(taskId)
   } catch (error) {
     logs.value = [{ time: formatTime(new Date()), message: error instanceof Error ? error.message : '任务日志加载失败', class: 'err' }]
   } finally {
@@ -129,10 +134,55 @@ async function loadLogs(taskId: string) {
   }
 }
 
+function startStream(taskId: string) {
+  stopStream() // 关闭之前的连接
+
+  eventSource = createTaskLogStream(taskId, {
+    onInit: (lines) => {
+      logs.value = lines
+      lastLoadedAt.value = new Date()
+      scrollToBottom()
+    },
+    onUpdate: (newLines) => {
+      logs.value = [...logs.value, ...newLines]
+      lastLoadedAt.value = new Date()
+      scrollToBottom()
+    },
+    onFinished: () => {
+      isStreaming.value = false
+    },
+    onError: (error) => {
+      console.error('SSE error:', error)
+      isStreaming.value = false
+    },
+  })
+
+  isStreaming.value = true
+}
+
+function stopStream() {
+  if (eventSource) {
+    eventSource.close()
+    eventSource = null
+    isStreaming.value = false
+  }
+}
+
+function scrollToBottom() {
+  // 延迟滚动，等待 DOM 更新
+  setTimeout(() => {
+    const logStream = document.querySelector('.log-stream')
+    if (logStream) {
+      logStream.scrollTop = logStream.scrollHeight
+    }
+  }, 50)
+}
+
 function selectTask(taskId: string) {
   if (selectedTaskId.value === taskId) {
     return
   }
+  stopStream() // 停止之前的流
   selectedTaskId.value = taskId
   void loadLogs(taskId)
 }
@@ -155,6 +205,10 @@ watch(
 onMounted(() => {
   void loadTasks()
 })
+
+onUnmounted(() => {
+  stopStream()
+})
 </script>
 
 <style scoped>
@@ -262,6 +316,17 @@ onMounted(() => {
   font-weight: 500;
 }
 
+.streaming-indicator {
+  font-size: 11px;
+  color: var(--accent);
+  animation: pulse 2s ease-in-out infinite;
+}
+
+@keyframes pulse {
+  0%, 100% { opacity: 1; }
+  50% { opacity: 0.5; }
+}
+
 .log-stream {
   max-height: calc(100vh - 210px);
   min-height: 520px;