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/services/scheduling/protocols.py

@@ -0,0 +1,146 @@
+"""调度/候选子组件的协议接口。
+
+目的：
+- 用 `Protocol` 固化 CacheAwareScheduler 的子组件契约
+- 便于单测注入 stub/mocks，减少对具体实现类的耦合
+
+说明：这里的协议面向“调度器内部协作”，因此保留了部分 `_` 前缀方法。
+后续如果要对外暴露更稳定的 API，可再抽出无下划线的 facade。
+"""
+
+from __future__ import annotations
+
+from typing import TYPE_CHECKING, Any, Protocol
+
+if TYPE_CHECKING:
+    from sqlalchemy.orm import Session
+
+    from src.models.database import GlobalModel, Provider, ProviderAPIKey
+    from src.services.scheduling.affinity_manager import CacheAffinity
+    from src.services.scheduling.schemas import ConcurrencySnapshot, ProviderCandidate
+
+
+class CandidateSorterProtocol(Protocol):
+    def _apply_priority_mode_sort(
+        self,
+        candidates: list[ProviderCandidate],
+        db: Session,
+        affinity_key: str | None = None,
+        api_format: str | None = None,
+    ) -> list[ProviderCandidate]: ...
+
+    def _apply_load_balance(
+        self, candidates: list[ProviderCandidate], api_format: str | None = None
+    ) -> list[ProviderCandidate]: ...
+
+    def shuffle_keys_by_internal_priority(
+        self,
+        keys: list[ProviderAPIKey],
+        affinity_key: str | None = None,
+        use_random: bool = False,
+    ) -> list[ProviderAPIKey]: ...
+
+
+class CandidateBuilderProtocol(Protocol):
+    def _query_provider_refs(
+        self,
+        db: Session,
+        provider_offset: int = 0,
+        provider_limit: int | None = None,
+    ) -> list[tuple[str, str]]: ...
+
+    def _query_providers(
+        self,
+        db: Session,
+        provider_offset: int = 0,
+        provider_limit: int | None = None,
+        allowed_providers: list[str] | None = None,
+        provider_ids: list[str] | None = None,
+    ) -> list[Provider]: ...
+
+    async def _build_candidates(
+        self,
+        db: Session,
+        providers: list[Provider],
+        client_format: str,
+        model_name: str,
+        affinity_key: str | None,
+        model_mappings: list[str] | None = None,
+        max_candidates: int | None = None,
+        is_stream: bool = False,
+        capability_requirements: dict[str, bool] | None = None,
+        global_conversion_enabled: bool = True,
+    ) -> list[ProviderCandidate]: ...
+
+    async def _check_model_support(
+        self,
+        db: Session,
+        provider: Provider,
+        model_name: str,
+        api_format: str | None = None,
+        is_stream: bool = False,
+        capability_requirements: dict[str, bool] | None = None,
+    ) -> tuple[bool, str | None, list[str] | None, set[str] | None]: ...
+
+    async def _check_model_support_for_global_model(
+        self,
+        db: Session,
+        provider: Provider,
+        global_model: GlobalModel,
+        model_name: str,
+        api_format: str | None = None,
+        is_stream: bool = False,
+        capability_requirements: dict[str, bool] | None = None,
+    ) -> tuple[bool, str | None, list[str] | None, set[str] | None]: ...
+
+    def _check_key_availability(
+        self,
+        key: ProviderAPIKey,
+        api_format: str | None,
+        model_name: str,
+        capability_requirements: dict[str, bool] | None = None,
+        model_mappings: list[str] | None = None,
+        candidate_models: set[str] | None = None,
+        *,
+        provider_type: str | None = None,
+    ) -> tuple[bool, str | None, str | None]: ...
+
+
+class ConcurrencyCheckerProtocol(Protocol):
+    async def check_available(
+        self,
+        key: ProviderAPIKey,
+        is_cached_user: bool = False,
+    ) -> tuple[bool, ConcurrencySnapshot]: ...
+
+    def get_reservation_stats(self) -> dict[str, Any]: ...
+
+
+class CacheAffinityManagerProtocol(Protocol):
+    async def get_affinity(
+        self, affinity_key: str, api_format: str, model_name: str
+    ) -> CacheAffinity | None: ...
+
+    async def set_affinity(
+        self,
+        affinity_key: str,
+        provider_id: str,
+        endpoint_id: str,
+        key_id: str,
+        api_format: str,
+        model_name: str,
+        supports_caching: bool = True,
+        ttl: int | None = None,
+    ) -> None: ...
+
+    async def invalidate_affinity(
+        self,
+        affinity_key: str,
+        api_format: str,
+        model_name: str,
+        key_id: str | None = None,
+        provider_id: str | None = None,
+        endpoint_id: str | None = None,
+    ) -> None: ...
+
+    def get_stats(self) -> dict[str, Any]: ...