添加provider工厂和Ollama支持

- 实现ProviderFactory用于构建不同类型的provider适配器
- 添加EnvironmentCredentialResolver用于解析环境变量中的凭证
- 实现OllamaProvider支持本地模型调用
- 实现OpenAICompatibleProvider支持OpenAI兼容接口
- 在AgentRuntime中添加对ProviderError的处理
- 更新Message结构体添加tool_calls字段
- 实现provider配置的增删改查API端点
- 添加provider注册表的replace方法
- 添加HTTP基础类和工具参数解码功能
- 更新依赖添加httpx库
- 添加相关单元测试验证provider适配器功能
```

backend/app/container.py

@@ -3,18 +3,21 @@ from dataclasses import dataclass
 from app.agent import AgentRuntime, PermissionManager, PermissionPolicy, ToolRegistry
 from app.agent.builtin_tools import register_builtin_tools
 from app.contracts import ModelCapability, ProviderConfig, ProviderType
-from app.providers import MockProvider, ProviderRegistry
+from app.providers import MockProvider, ProviderFactory, ProviderRegistry
+from app.providers.credentials import EnvironmentCredentialResolver
 
 
 @dataclass(frozen=True)
 class ApplicationContainer:
     providers: ProviderRegistry
+    provider_factory: ProviderFactory
     tools: ToolRegistry
     permissions: PermissionManager
     agent: AgentRuntime
 
 
 def build_container() -> ApplicationContainer:
+    provider_factory = ProviderFactory(EnvironmentCredentialResolver())
     providers = ProviderRegistry()
     providers.register(
         ProviderConfig(
@@ -40,6 +43,7 @@ def build_container() -> ApplicationContainer:
     agent = AgentRuntime(providers=providers, tools=tools, permissions=permissions)
     return ApplicationContainer(
         providers=providers,
+        provider_factory=provider_factory,
         tools=tools,
         permissions=permissions,
         agent=agent,