feat: 重构前后端架构，添加Go后端和Python Agent服务

- 新增 Go 语言后端服务(server/)，包含用户认证、Agent管理、数据库连接等API
- 新增 Python Agent 服务(agent/)，实现Agent核心逻辑和工具集
- 前端从原生HTML迁移到Vue.js框架(web/src/)
- 添加 Docker Compose 支持(docker-compose.yml)
- 添加项目架构文档(docs/ARCHITECTURE.md)
- 添加环境变量示例(.env.example)和本地启动脚本(start-local.ps1)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

agent/app/agent/tools/impl/search.py

@@ -0,0 +1,87 @@
+"""
+网页搜索工具
+"""
+import httpx
+from typing import Optional
+
+
+async def search_web(query: str, max_results: int = 5) -> dict:
+    """
+    搜索网页获取信息
+
+    Args:
+        query: 搜索关键词
+        max_results: 返回结果数量
+
+    Returns:
+        搜索结果
+    """
+    # 这里可以使用搜索引擎API，如 Google, Bing, DuckDuckGo 等
+    # 示例使用 DuckDuckGo API（免费）
+
+    try:
+        async with httpx.AsyncClient() as client:
+            response = await client.get(
+                "https://api.duckduckgo.com/",
+                params={
+                    "q": query,
+                    "format": "json",
+                    "no_html": 1,
+                    "skip_disambig": 1
+                },
+                timeout=10.0
+            )
+
+            if response.status_code == 200:
+                data = response.json()
+                results = []
+
+                # 提取相关主题
+                if "RelatedTopics" in data:
+                    for item in data["RelatedTopics"][:max_results]:
+                        if "Text" in item:
+                            results.append({
+                                "title": item.get("Text", "").split(" - ")[0] if " - " in item.get("Text", "") else "",
+                                "content": item.get("Text", ""),
+                                "url": item.get("URL", "")
+                            })
+
+                return {
+                    "success": True,
+                    "query": query,
+                    "results": results,
+                    "count": len(results)
+                }
+            else:
+                return {
+                    "success": False,
+                    "error": f"Search API returned status {response.status_code}"
+                }
+
+    except Exception as e:
+        return {
+            "success": False,
+            "error": str(e)
+        }
+
+
+# 工具定义（用于 LLM）
+TOOL_DEFINITION = {
+    "name": "search",
+    "description": "Search the web for information. Use this when you need to find current information or facts.",
+    "parameters": {
+        "type": "object",
+        "properties": {
+            "query": {
+                "type": "string",
+                "description": "The search query"
+            },
+            "max_results": {
+                "type": "integer",
+                "description": "Maximum number of results to return",
+                "default": 5
+            }
+        },
+        "required": ["query"]
+    }
+}