chore: 初始版本提交 - 简化架构 + 轮询改造

- 移除 Motia Streams 实时通信，改用 3 秒轮询
- 简化前端代码，移除冗余组件
- 简化后端架构，准备 FastAPI 重构
- 更新 pixi.toml 环境配置
- 保留 bttoxin_digger_v5_repro 作为参考文档

Co-Authored-By: Claude <noreply@anthropic.com>

frontend/src/App.vue

@@ -1,21 +1,11 @@
 <script setup lang="ts">
-import { ref, provide, readonly } from 'vue'
-
 /**
  * App.vue - Main application layout
- * Requirements: 6.1 - Display connection status indicator
+ * Simplified for polling-based implementation
  */
 
-// Connection status state - will be updated by useMotiaStreams composable
-const isConnected = ref(true)
-
-// Provide connection status to child components
-provide('connectionStatus', {
-  isConnected: readonly(isConnected),
-  setConnected: (value: boolean) => {
-    isConnected.value = value
-  },
-})
+// Header icon component
+import { Monitor } from '@element-plus/icons-vue'
 </script>
 
 <template>
@@ -24,18 +14,11 @@ provide('connectionStatus', {
       <div class="header-content">
         <div class="logo">
           <el-icon :size="24"><Monitor /></el-icon>
-          <span class="title">BtToxin Task Monitor</span>
+          <span class="title">BtToxin Pipeline</span>
         </div>
-        <div class="connection-status">
-          <el-tag
-            :type="isConnected ? 'success' : 'danger'"
-            effect="light"
-            size="small"
-          >
-            <el-icon class="status-icon">
-              <component :is="isConnected ? 'CircleCheck' : 'CircleClose'" />
-            </el-icon>
-            {{ isConnected ? 'Connected' : 'Disconnected' }}
+        <div class="header-tag">
+          <el-tag type="success" effect="light" size="small">
+            基因组毒素分析系统
           </el-tag>
         </div>
       </div>
@@ -80,15 +63,11 @@ provide('connectionStatus', {
   font-weight: 600;
 }
 
-.connection-status {
+.header-tag {
   display: flex;
   align-items: center;
 }
 
-.status-icon {
-  margin-right: 4px;
-}
-
 .app-main {
   padding: 20px;
   max-width: 1200px;