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/admin/models/write.rs

@@ -1,4 +1,22 @@
-use super::*;
+use super::super::{normalize_json_array, normalize_json_object, normalize_string_list};
+use super::{
+    admin_provider_model_effective_capability, admin_provider_model_effective_input_price,
+    admin_provider_model_effective_output_price, admin_provider_model_name_exists,
+    normalize_optional_price, normalize_required_trimmed_string,
+    resolve_admin_global_model_by_id_or_err,
+};
+use crate::gateway::handlers::{
+    AdminGlobalModelCreateRequest, AdminGlobalModelUpdateRequest, AdminImportProviderModelsRequest,
+    AdminProviderModelCreateRequest, AdminProviderModelUpdateRequest,
+};
+use crate::gateway::AppState;
+use aether_data::repository::global_models::{
+    AdminProviderModelListQuery, CreateAdminGlobalModelRecord, StoredAdminGlobalModel,
+    StoredAdminProviderModel, UpdateAdminGlobalModelRecord, UpsertAdminProviderModelRecord,
+};
+use serde_json::json;
+use std::collections::{BTreeMap, BTreeSet};
+use uuid::Uuid;
 
 pub(crate) async fn build_admin_global_model_create_record(
     state: &AppState,