refactor: 移除 Python upstream 依赖，清理全部 legacy/Python 兼容层

- 移除 upstream_base_url 参数及 AETHER_GATEWAY_UPSTREAM 环境变量，gateway 不再需要指向 Python 宿主
- 删除所有 LEGACY_*/PYTHON_* 常量、路由组、header 定义及 sunset/phaseout 机制
- 将 legacy_gateway_bridge 重命名为 internal_gateway，executor 相关命名统一为 execution_runtime
- dev.sh 新增 Postgres/Redis 预检查，移除 upstream 相关启动参数和提示
- 新增 ai_public 路由处理器
- 全量适配 handler、test、state、control 等模块的命名和接口变更

apps/aether-gateway/src/maintenance/runtime/schedule.rs

@@ -1,4 +1,17 @@
-use super::*;
+use std::time::Duration;
+
+use chrono::{DateTime, Datelike, TimeZone, Timelike, Utc, Weekday};
+use chrono_tz::Tz;
+use tracing::warn;
+
+use crate::gateway::gateway_data::GatewayDataState;
+
+use super::{
+    system_config_string, WalletDailyUsageAggregationTarget, DB_MAINTENANCE_HOUR,
+    DB_MAINTENANCE_MINUTE, DB_MAINTENANCE_WEEKDAY, DB_MAINTENANCE_WEEKLY_INTERVAL,
+    MAINTENANCE_DEFAULT_TIMEZONE, PROVIDER_CHECKIN_DEFAULT_TIME, STATS_DAILY_AGGREGATION_HOUR,
+    STATS_DAILY_AGGREGATION_MINUTE, STATS_HOURLY_AGGREGATION_MINUTE,
+};
 
 pub(super) async fn provider_checkin_schedule(
     data: &GatewayDataState,