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/video_tasks/store.rs

@@ -0,0 +1,20 @@
+use super::*;
+
+mod backend;
+mod registry;
+
+pub(crate) use self::backend::{FileVideoTaskStore, InMemoryVideoTaskStore};
+use self::registry::VideoTaskRegistry;
+
+pub(super) trait VideoTaskStore: std::fmt::Debug + Send + Sync {
+    fn insert(&self, snapshot: LocalVideoTaskSnapshot);
+    fn read_openai(&self, task_id: &str) -> Option<LocalVideoTaskReadResponse>;
+    fn read_gemini(&self, short_id: &str) -> Option<LocalVideoTaskReadResponse>;
+    fn clone_openai(&self, task_id: &str) -> Option<OpenAiVideoTaskSeed>;
+    fn clone_gemini(&self, short_id: &str) -> Option<GeminiVideoTaskSeed>;
+    #[cfg(test)]
+    fn list_active_snapshots(&self, limit: usize) -> Vec<LocalVideoTaskSnapshot>;
+    fn apply_mutation(&self, mutation: LocalVideoTaskRegistryMutation);
+    fn project_openai(&self, task_id: &str, provider_body: &Map<String, Value>) -> bool;
+    fn project_gemini(&self, short_id: &str, provider_body: &Map<String, Value>) -> bool;
+}