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/models/api_key.py

@@ -0,0 +1,64 @@
+"""
+Provider API Key相关的API模型
+"""
+
+from datetime import datetime
+
+from pydantic import BaseModel, ConfigDict, Field
+
+
+class ProviderAPIKeyBase(BaseModel):
+    """Provider API Key基础模型"""
+
+    name: str | None = Field(None, description="密钥名称/备注")
+    api_key: str = Field(..., description="API密钥")
+    rpm_limit: int | None = Field(None, description="RPM限制（每分钟请求数），NULL=自适应模式")
+    priority: int = Field(0, description="优先级（越高越优先使用）")
+    is_active: bool = Field(True, description="是否启用")
+    expires_at: datetime | None = Field(None, description="过期时间")
+
+
+class ProviderAPIKeyCreate(ProviderAPIKeyBase):
+    """创建Provider API Key请求"""
+
+    pass
+
+
+class ProviderAPIKeyUpdate(BaseModel):
+    """更新Provider API Key请求"""
+
+    name: str | None = None
+    api_key: str | None = None
+    rpm_limit: int | None = None
+    priority: int | None = None
+    is_active: bool | None = None
+    expires_at: datetime | None = None
+
+
+class ProviderAPIKeyResponse(ProviderAPIKeyBase):
+    """Provider API Key响应"""
+
+    id: str
+    provider_id: str
+    request_count: int | None = Field(0, description="请求次数")
+    error_count: int | None = Field(0, description="错误次数")
+    last_used_at: datetime | None = Field(None, description="最后使用时间")
+    last_error_at: datetime | None = Field(None, description="最后错误时间")
+    last_error_msg: str | None = Field(None, description="最后错误信息")
+    created_at: datetime
+    updated_at: datetime
+
+    model_config = ConfigDict(from_attributes=True)
+
+
+class ProviderAPIKeyStats(BaseModel):
+    """Provider API Key统计信息"""
+
+    id: str
+    name: str | None
+    request_count: int
+    error_count: int
+    success_rate: float
+    last_used_at: datetime | None
+    is_active: bool
+    is_expired: bool