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/utils/perf.py

@@ -0,0 +1,135 @@
+from __future__ import annotations
+
+import random
+import time
+from typing import Any
+
+from src.config.settings import config
+from src.core.logger import logger
+
+
+class PerfRecorder:
+    """轻量性能记录器（可选启用）"""
+
+    @staticmethod
+    def enabled() -> bool:
+        return bool(config.perf_metrics_enabled or config.perf_log_slow_ms > 0)
+
+    @staticmethod
+    def start(force: bool = False) -> float | None:
+        if not force and not PerfRecorder.enabled():
+            return None
+        return time.perf_counter()
+
+    @staticmethod
+    def stop(
+        start: float | None,
+        name: str,
+        labels: dict[str, str] | None = None,
+        *,
+        sample_rate: float | None = None,
+        log_hint: str | None = None,
+    ) -> float | None:
+        if start is None:
+            return None
+        duration = time.perf_counter() - start
+        PerfRecorder.record_timing(
+            name,
+            duration,
+            labels=labels,
+            sample_rate=sample_rate,
+            log_hint=log_hint,
+        )
+        return duration
+
+    @staticmethod
+    def record_timing(
+        name: str,
+        duration: float,
+        labels: dict[str, str] | None = None,
+        *,
+        sample_rate: float | None = None,
+        log_hint: str | None = None,
+    ) -> None:
+        if not PerfRecorder.enabled():
+            return
+        if not PerfRecorder._should_sample(sample_rate):
+            return
+
+        duration_ms = duration * 1000.0
+        if config.perf_log_slow_ms > 0 and duration_ms >= float(config.perf_log_slow_ms):
+            hint = f" | {log_hint}" if log_hint else ""
+            logger.info("[PERF] {} took {:.2f}ms{}", name, duration_ms, hint)
+
+        if not config.perf_metrics_enabled:
+            return
+
+        plugin = PerfRecorder._get_monitor_plugin()
+        if not plugin:
+            return
+        PerfRecorder._create_task(plugin.timing(PerfRecorder._metric_name(name), duration, labels))
+
+    @staticmethod
+    def record_counter(
+        name: str,
+        value: float = 1,
+        labels: dict[str, str] | None = None,
+        *,
+        sample_rate: float | None = None,
+    ) -> None:
+        if not config.perf_metrics_enabled:
+            return
+        if not PerfRecorder._should_sample(sample_rate):
+            return
+
+        plugin = PerfRecorder._get_monitor_plugin()
+        if not plugin:
+            return
+        PerfRecorder._create_task(
+            plugin.increment(PerfRecorder._metric_name(name), value=value, labels=labels)
+        )
+
+    @staticmethod
+    def should_store() -> bool:
+        return bool(getattr(config, "perf_store_enabled", False))
+
+    @staticmethod
+    def should_store_sample() -> bool:
+        if not PerfRecorder.should_store():
+            return False
+        rate = float(getattr(config, "perf_store_sample_rate", 1.0))
+        return PerfRecorder._should_sample(rate)
+
+    @staticmethod
+    def _should_sample(sample_rate: float | None) -> bool:
+        rate = float(sample_rate if sample_rate is not None else config.perf_sample_rate)
+        if rate >= 1:
+            return True
+        if rate <= 0:
+            return False
+        return random.random() < rate
+
+    @staticmethod
+    def _get_monitor_plugin() -> Any | None:
+        # Lazy import to avoid circular deps during app startup.
+        try:
+            from src.plugins.manager import get_plugin_manager
+        except Exception:
+            return None
+        try:
+            plugin = get_plugin_manager().get_plugin("monitor")
+        except Exception:
+            return None
+        if plugin and getattr(plugin, "enabled", True):
+            return plugin
+        return None
+
+    @staticmethod
+    def _metric_name(name: str) -> str:
+        return name if name.startswith("perf_") else f"perf_{name}"
+
+    @staticmethod
+    def _create_task(coro: Any) -> None:
+        from src.utils.async_utils import safe_create_task
+
+        safe_create_task(coro)