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/plugins/auth/base.py

@@ -0,0 +1,122 @@
+"""
+认证插件基类
+定义认证插件的接口和认证上下文
+"""
+
+from __future__ import annotations
+
+from abc import abstractmethod
+from dataclasses import dataclass
+from typing import Any
+
+from fastapi import Request
+from sqlalchemy.orm import Session
+
+from ..common import BasePlugin
+
+
+@dataclass
+class AuthContext:
+    """
+    认证上下文
+    包含认证后的用户信息和权限
+    """
+
+    user_id: int
+    user_name: str
+    api_key_id: int | None = None
+    api_key_name: str | None = None
+    permissions: dict[str, bool] = None
+    billing_info: dict[str, Any] = None
+    metadata: dict[str, Any] = None
+
+    def __post_init__(self) -> None:
+        if self.permissions is None:
+            self.permissions = {}
+        if self.metadata is None:
+            self.metadata = {}
+
+
+class AuthPlugin(BasePlugin):
+    """
+    认证插件基类
+    所有认证插件必须继承此类并实现authenticate方法
+    """
+
+    def __init__(
+        self,
+        name: str,
+        priority: int = 0,
+        version: str = "1.0.0",
+        author: str = "Unknown",
+        description: str = "",
+        api_version: str = "1.0",
+        dependencies: list[str] | None = None,
+        provides: list[str] | None = None,
+        config: dict[str, Any] | None = None,
+    ):
+        """
+        初始化认证插件
+
+        Args:
+            name: 插件名称
+            priority: 优先级（数字越大优先级越高）
+            version: 插件版本
+            author: 插件作者
+            description: 插件描述
+            api_version: API版本
+            dependencies: 依赖的其他插件
+            provides: 提供的服务
+            config: 配置字典
+        """
+        super().__init__(
+            name=name,
+            priority=priority,
+            version=version,
+            author=author,
+            description=description,
+            api_version=api_version,
+            dependencies=dependencies,
+            provides=provides,
+            config=config,
+        )
+
+    @abstractmethod
+    async def authenticate(self, request: Request, db: Session) -> AuthContext | None:
+        """
+        执行认证
+
+        Args:
+            request: FastAPI请求对象
+            db: 数据库会话
+
+        Returns:
+            成功返回AuthContext，失败返回None
+        """
+        pass
+
+    @abstractmethod
+    def get_credentials(self, request: Request) -> str | None:
+        """
+        从请求中提取认证凭据
+
+        Args:
+            request: FastAPI请求对象
+
+        Returns:
+            认证凭据字符串，如果没有找到返回None
+        """
+        pass
+
+    def is_applicable(self, request: Request) -> bool:
+        """
+        检查此插件是否适用于当前请求
+
+        Args:
+            request: FastAPI请求对象
+
+        Returns:
+            如果插件适用返回True
+        """
+        # 默认情况下，如果能提取到凭据就适用
+        return self.get_credentials(request) is not None