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/admin/stats/time_series.py

@@ -0,0 +1,93 @@
+"""Admin time series stats routes."""
+
+from __future__ import annotations
+
+from datetime import date
+from typing import Any, Literal
+
+from fastapi import APIRouter, Depends, HTTPException, Query, Request
+from sqlalchemy.orm import Session
+
+from src.api.base.admin_adapter import AdminApiAdapter
+from src.api.base.context import ApiRequestContext
+from src.config.constants import CacheTTL
+from src.database import get_db
+from src.services.system.stats_aggregator import TimeSeriesFilter, query_time_series
+from src.services.system.time_range import TimeRangeParams
+from src.utils.cache_decorator import cache_result
+
+from .common import _apply_admin_default_range, _build_time_range_params, pipeline
+
+router = APIRouter()
+
+
+class AdminTimeSeriesAdapter(AdminApiAdapter):
+    def __init__(
+        self,
+        time_range: TimeRangeParams | None,
+        user_id: str | None,
+        model: str | None,
+        provider_name: str | None,
+    ) -> None:
+        self.time_range = _apply_admin_default_range(time_range)
+        self.user_id = user_id
+        self.model = model
+        self.provider_name = provider_name
+
+    @cache_result(
+        key_prefix="admin:stats:time_series",
+        ttl=CacheTTL.ADMIN_USAGE_AGGREGATION,
+        user_specific=False,
+        vary_by=[
+            "time_range.start_date",
+            "time_range.end_date",
+            "time_range.preset",
+            "time_range.timezone",
+            "time_range.tz_offset_minutes",
+            "time_range.granularity",
+            "user_id",
+            "model",
+            "provider_name",
+        ],
+    )
+    async def handle(self, context: ApiRequestContext) -> Any:  # type: ignore[override]
+        if not self.time_range:
+            return []
+        try:
+            return query_time_series(
+                context.db,
+                self.time_range,
+                filters=TimeSeriesFilter(
+                    user_id=self.user_id, model=self.model, provider_name=self.provider_name
+                ),
+            )
+        except ValueError as exc:
+            raise HTTPException(status_code=400, detail=str(exc)) from exc
+
+
+@router.get("/time-series")
+async def get_time_series(
+    request: Request,
+    db: Session = Depends(get_db),
+    start_date: date | None = Query(None),
+    end_date: date | None = Query(None),
+    preset: str | None = Query(None),
+    granularity: Literal["hour", "day", "week", "month"] = Query("day"),
+    timezone_name: str | None = Query(None, alias="timezone"),
+    tz_offset_minutes: int | None = Query(0),
+    user_id: str | None = Query(None),
+    model: str | None = Query(None),
+    provider_name: str | None = Query(None),
+) -> Any:
+    time_range = _build_time_range_params(
+        start_date, end_date, preset, timezone_name, tz_offset_minutes
+    )
+    if time_range:
+        time_range.granularity = granularity
+    adapter = AdminTimeSeriesAdapter(
+        time_range=time_range,
+        user_id=user_id,
+        model=model,
+        provider_name=provider_name,
+    )
+    return await pipeline.run(adapter=adapter, http_request=request, db=db, mode=adapter.mode)