refactor: 移除 Python 后端源码，全面迁移至 Rust gateway 架构

- 删除全部 Python 源码 (src/) 及 Alembic 迁移脚本，归档至 _deprecated_py_src/
- 重构 Rust gateway ai_pipeline: 拆分 planner/finalize 模块，新增 contracts/adaptation 层
- 重组 handlers 模块为 admin/public/proxy/internal/shared 子模块结构
- 新增 executor 模块，引入 Rust 原生数据库迁移 (aether-data/migrations)
- 简化 CI/Docker 构建流程，移除 base image 二级构建，统一为单一 app image
- 移除 Python 相关基础设施文件 (entrypoint.sh, gunicorn_conf.py, Dockerfile.base)

_deprecated_py_src/api/handlers/openai/adapter.py

@@ -0,0 +1,123 @@
+"""
+OpenAI Chat Adapter - 基于 ChatAdapterBase 的 OpenAI Chat API 适配器
+
+处理 /v1/chat/completions 端点的 OpenAI Chat 格式请求。
+"""
+
+from __future__ import annotations
+
+from typing import Any
+
+from fastapi.responses import JSONResponse
+
+from src.api.handlers.base.chat_adapter_base import ChatAdapterBase, register_adapter
+from src.api.handlers.base.chat_handler_base import ChatHandlerBase
+from src.core.api_format import ApiFamily
+from src.core.logger import logger
+from src.models.openai import OpenAIRequest
+
+
+@register_adapter
+class OpenAIChatAdapter(ChatAdapterBase):
+    """
+    OpenAI Chat Completions API 适配器
+
+    处理 OpenAI Chat 格式的请求（/v1/chat/completions 端点）。
+    """
+
+    FORMAT_ID = "openai:chat"
+    API_FAMILY = ApiFamily.OPENAI
+    name = "openai.chat"
+
+    @property
+    def HANDLER_CLASS(self) -> type[ChatHandlerBase]:
+        """延迟导入 Handler 类避免循环依赖"""
+        from src.api.handlers.openai.handler import OpenAIChatHandler
+
+        return OpenAIChatHandler
+
+    def __init__(self, allowed_api_formats: list[str] | None = None):
+        super().__init__(allowed_api_formats)
+
+    def _validate_request_body(
+        self, original_request_body: dict, path_params: dict | None = None
+    ) -> None:
+        """验证请求体"""
+        if not isinstance(original_request_body, dict):
+            return self._error_response(
+                400, "Request body must be a JSON object", "invalid_request_error"
+            )
+
+        required_fields = ["model", "messages"]
+        missing = [f for f in required_fields if f not in original_request_body]
+        if missing:
+            return self._error_response(
+                400,
+                f"Missing required fields: {', '.join(missing)}",
+                "invalid_request_error",
+            )
+
+        try:
+            return OpenAIRequest.model_validate(original_request_body, strict=False)
+        except ValueError as e:
+            return self._error_response(400, str(e), "invalid_request_error")
+        except Exception as e:
+            logger.warning(f"Pydantic验证警告(将继续处理): {str(e)}")
+            return OpenAIRequest.model_construct(
+                model=original_request_body.get("model"),
+                messages=original_request_body.get("messages", []),
+                stream=original_request_body.get("stream", False),
+                max_tokens=original_request_body.get("max_tokens"),
+            )
+
+    def _build_audit_metadata(self, payload: dict[str, Any], request_obj: Any) -> dict[str, Any]:
+        """构建 OpenAI Chat 特定的审计元数据"""
+        role_counts = {}
+        for message in request_obj.messages:
+            role_counts[message.role] = role_counts.get(message.role, 0) + 1
+
+        return {
+            "action": "openai_chat_completion",
+            "model": request_obj.model,
+            "stream": bool(request_obj.stream),
+            "max_tokens": request_obj.max_tokens,
+            "temperature": request_obj.temperature,
+            "top_p": request_obj.top_p,
+            "messages_count": len(request_obj.messages),
+            "message_roles": role_counts,
+            "tools_count": len(request_obj.tools or []),
+            "response_format": bool(request_obj.response_format),
+            "user_identifier": request_obj.user,
+        }
+
+    def _error_response(self, status_code: int, message: str, error_type: str) -> JSONResponse:
+        """生成 OpenAI 格式的错误响应"""
+        return JSONResponse(
+            status_code=status_code,
+            content={
+                "error": {
+                    "type": error_type,
+                    "message": message,
+                    "code": status_code,
+                }
+            },
+        )
+
+    @classmethod
+    def build_endpoint_url(
+        cls,
+        base_url: str,
+        request_data: dict[str, Any] | None = None,
+        model_name: str | None = None,
+        *,
+        provider_type: str | None = None,
+    ) -> str:
+        """构建OpenAI API端点URL"""
+        base_url = base_url.rstrip("/")
+        if base_url.endswith("/v1"):
+            return f"{base_url}/chat/completions"
+        else:
+            return f"{base_url}/v1/chat/completions"
+
+
+__all__ = ["OpenAIChatAdapter"]