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/llm/factory.py

@@ -0,0 +1,63 @@
+"""
+LLM 工厂 - 创建不同提供商的 LLM 实例
+"""
+from typing import Optional
+from langchain_openai import ChatOpenAI
+from langchain_anthropic import ChatAnthropic
+
+
+class LLMFactory:
+    """LLM 工厂类"""
+
+    def __init__(
+        self,
+        provider: str = "openai",
+        openai_api_key: Optional[str] = None,
+        anthropic_api_key: Optional[str] = None,
+        model: str = "gpt-3.5-turbo",
+        temperature: float = 0.7,
+        max_tokens: int = 2000
+    ):
+        self.provider = provider
+        self.openai_api_key = openai_api_key
+        self.anthropic_api_key = anthropic_api_key
+        self.model = model
+        self.temperature = temperature
+        self.max_tokens = max_tokens
+
+        self._llm = None
+
+    def get_llm(self):
+        """获取 LLM 实例"""
+        if self._llm is not None:
+            return self._llm
+
+        if self.provider == "openai":
+            self._llm = ChatOpenAI(
+                model=self.model,
+                temperature=self.temperature,
+                max_tokens=self.max_tokens,
+                api_key=self.openai_api_key
+            )
+        elif self.provider == "anthropic":
+            self._llm = ChatAnthropic(
+                model=self.model,
+                temperature=self.temperature,
+                max_tokens=self.max_tokens,
+                anthropic_api_key=self.anthropic_api_key
+            )
+        else:
+            raise ValueError(f"Unsupported provider: {self.provider}")
+
+        return self._llm
+
+    def set_model(self, model: str):
+        """设置模型"""
+        self.model = model
+        self._llm = None  # 重置 LLM 实例
+
+    def set_temperature(self, temperature: float):
+        """设置温度"""
+        self.temperature = temperature
+        if self._llm:
+            self._llm.temperature = temperature