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>

motia-backend/package.json

@@ -0,0 +1,25 @@
+{
+  "name": "bttoxin-motia-backend",
+  "version": "1.0.0",
+  "description": "Motia backend for BtToxin task workflow monitor",
+  "type": "module",
+  "scripts": {
+    "dev": "motia dev",
+    "build": "motia build",
+    "start": "motia start",
+    "test": "vitest run",
+    "test:watch": "vitest"
+  },
+  "dependencies": {
+    "@motia/core": "^0.1.0",
+    "uuid": "^9.0.0",
+    "zod": "^3.22.0"
+  },
+  "devDependencies": {
+    "@types/node": "^20.10.0",
+    "@types/uuid": "^9.0.0",
+    "typescript": "^5.3.0",
+    "vitest": "^1.0.0",
+    "fast-check": "^3.15.0"
+  }
+}