refactor: 大规模模块拆分与代码精简，新增 ai-pipeline/data-contracts 独立 crate

- 新增 aether-ai-pipeline 和 aether-data-contracts crate，将 pipeline 逻辑与数据契约从 gateway 中解耦
- 重构 admin handlers：拆分单体模块为 auth/billing/endpoint/features/model/observability/provider/system 等独立子模块
- 合并 chat/cli 重复代码路径：精简 conversion、finalize、planner 中的 sync/chat/cli 分支
- 重构 scheduler/executor/data 层，引入 facade 模式降低模块间耦合
- 移除冗余的 intent 模块，将 plan_fallback/policy/stream_path/sync_path 迁移至 executor
- 前端适配：调整 admin API 调用和 provider 模型测试对话框

apps/aether-gateway/src/handlers/public/mod.rs

@@ -14,24 +14,14 @@ pub(crate) use self::catalog_helpers::{
     ApiFormatHealthMonitorOptions,
 };
 pub(crate) use self::system_modules_helpers::{
-    admin_module_by_name, admin_module_name_from_enabled_path, admin_module_name_from_status_path,
-    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_keys_grouped_by_format_payload, build_admin_module_runtime_state,
-    build_admin_module_status_payload, build_admin_module_validation_result,
-    build_admin_modules_status_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,
-    build_public_auth_modules_status_payload, capability_detail_by_name, current_aether_version,
-    delete_admin_system_config, enabled_key_capability_short_names,
-    escape_admin_email_template_html, ldap_module_config_is_valid, 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, serialize_public_capability,
-    supported_capability_names, system_config_bool, system_config_string,
-    AdminSetModuleEnabledRequest, PUBLIC_CAPABILITY_DEFINITIONS,
+    apply_admin_email_template_update, build_admin_email_template_payload,
+    build_admin_email_templates_payload, build_admin_keys_grouped_by_format_payload,
+    build_public_auth_modules_status_payload, capability_detail_by_name,
+    enabled_key_capability_short_names, escape_admin_email_template_html,
+    ldap_module_config_is_valid, module_available_from_env, preview_admin_email_template,
+    read_admin_email_template_payload, render_admin_email_template_html,
+    reset_admin_email_template, serialize_public_capability, supported_capability_names,
+    system_config_bool, system_config_string, PUBLIC_CAPABILITY_DEFINITIONS,
 };
 
 pub(crate) use self::support::{