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/handlers/public/system_modules_helpers.rs

@@ -1,5 +1,3 @@
-pub(crate) use super::*;
-
 #[path = "system_modules_helpers/capabilities.rs"]
 mod system_modules_capabilities;
 #[path = "system_modules_helpers/keys_grouped.rs"]
@@ -9,7 +7,28 @@ mod system_modules_modules;
 #[path = "system_modules_helpers/system.rs"]
 mod system_modules_system;
 
-pub(crate) use self::system_modules_capabilities::*;
-pub(crate) use self::system_modules_keys_grouped::*;
-pub(crate) use self::system_modules_modules::*;
-pub(crate) use self::system_modules_system::*;
+pub(crate) use self::system_modules_capabilities::{
+    capability_detail_by_name, enabled_key_capability_short_names, serialize_public_capability,
+    supported_capability_names, PUBLIC_CAPABILITY_DEFINITIONS,
+};
+pub(crate) use self::system_modules_keys_grouped::build_admin_keys_grouped_by_format_payload;
+pub(crate) use self::system_modules_modules::{
+    admin_module_by_name, admin_module_name_from_enabled_path, admin_module_name_from_status_path,
+    build_admin_module_runtime_state, build_admin_module_status_payload,
+    build_admin_module_validation_result, build_admin_modules_status_payload,
+    build_public_auth_modules_status_payload, ldap_module_config_is_valid,
+    AdminSetModuleEnabledRequest,
+};
+pub(crate) use self::system_modules_system::{
+    apply_admin_email_template_update, apply_admin_system_config_update,
+    apply_admin_system_settings_update, build_admin_api_formats_payload,
+    build_admin_email_template_payload, build_admin_email_templates_payload,
+    build_admin_system_check_update_payload, build_admin_system_config_detail_payload,
+    build_admin_system_config_export_payload, build_admin_system_configs_payload,
+    build_admin_system_settings_payload, build_admin_system_stats_payload,
+    build_admin_system_users_export_payload, current_aether_version, delete_admin_system_config,
+    escape_admin_email_template_html, module_available_from_env, preview_admin_email_template,
+    read_admin_email_template_payload, render_admin_email_template_html,
+    reset_admin_email_template, serialize_admin_system_users_export_wallet, system_config_bool,
+    system_config_string,
+};