refactor: 移除独立 hub/proxy/executor/gateway crate，统一为 gateway tunnel 架构

- 删除 aether-hub、aether-proxy 独立项目及其 Dockerfile/配置
- 删除 crates/aether-executor 和 crates/aether-gateway 全部模块
- 新增 apps/ 目录作为应用入口
- 将 hub 概念重构为 gateway tunnel transport
- 将 executor 重构为 execution runtime
- 新增 tunnel.rs 合约定义和 testkit tunnel/execution_runtime 模块
- 更新 Python 服务层和测试适配新架构命名

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

@@ -0,0 +1,59 @@
+use super::*;
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub(super) struct DbMaintenanceRunSummary {
+    pub(super) attempted: usize,
+    pub(super) succeeded: usize,
+}
+
+pub(super) async fn perform_db_maintenance_once(
+    data: &GatewayDataState,
+) -> Result<DbMaintenanceRunSummary, aether_data::DataLayerError> {
+    let Some(pool) = data.postgres_pool() else {
+        return Ok(DbMaintenanceRunSummary {
+            attempted: 0,
+            succeeded: 0,
+        });
+    };
+
+    run_db_maintenance_with(data, |table_name| {
+        let pool = pool.clone();
+        async move {
+            let statement = format!("VACUUM ANALYZE {table_name}");
+            sqlx::raw_sql(&statement).execute(&pool).await?;
+            Ok(())
+        }
+    })
+    .await
+}
+
+pub(super) async fn run_db_maintenance_with<F, Fut>(
+    data: &GatewayDataState,
+    mut vacuum_table: F,
+) -> Result<DbMaintenanceRunSummary, aether_data::DataLayerError>
+where
+    F: FnMut(&'static str) -> Fut,
+    Fut: std::future::Future<Output = Result<(), aether_data::DataLayerError>>,
+{
+    if !system_config_bool(data, "enable_db_maintenance", true).await? {
+        return Ok(DbMaintenanceRunSummary {
+            attempted: 0,
+            succeeded: 0,
+        });
+    }
+
+    let mut summary = DbMaintenanceRunSummary {
+        attempted: 0,
+        succeeded: 0,
+    };
+    for table_name in DB_MAINTENANCE_TABLES {
+        summary.attempted += 1;
+        match vacuum_table(table_name).await {
+            Ok(()) => summary.succeeded += 1,
+            Err(err) => {
+                warn!(table = table_name, error = %err, "gateway db maintenance table failed");
+            }
+        }
+    }
+    Ok(summary)
+}