feat(gateway): 重构 usage 数据层、迁移系统与系统导入

数据库迁移:
- 引入 baseline v2 bootstrap，空库首次启动自动初始化
- 服务启动不再自动执行迁移，需显式 `--migrate` 运行
- 新增 pending migration 检测，schema 落后时拒绝启动

Usage 数据层:
- usage body 存储外部化为独立 blob 表
- 新增 HTTP audit 表拆分存储请求/响应头与 body ref
- 后台清理任务支持 legacy body ref 元数据迁移
- usage runtime 写入迁移到专用 tokio runtime（独立线程池, 8MB 栈）

系统导入/导出:
- 支持用户、API Keys、钱包数据的完整导入
- 兼容 legacy 与 v1.3+ 两种导出格式

其他改进:
- executor outcome 增加 runtime miss 诊断上下文
- 主 tokio runtime 栈大小调整为 8MB
- 前端 provider 管理支持 base URL 配置
- dev.sh 支持 --migrate 参数

crates/aether-data/src/repository/usage/mod.rs

@@ -9,3 +9,92 @@ pub(crate) use aether_data_contracts::repository::usage::{
 };
 pub use memory::InMemoryUsageReadRepository;
 pub use sql::SqlxUsageReadRepository;
+
+pub(crate) fn strip_deprecated_usage_display_fields(
+    mut usage: UpsertUsageRecord,
+) -> UpsertUsageRecord {
+    usage.username = None;
+    usage.api_key_name = None;
+    usage
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{strip_deprecated_usage_display_fields, UpsertUsageRecord};
+
+    #[test]
+    fn strip_deprecated_usage_display_fields_clears_legacy_display_columns() {
+        let usage = strip_deprecated_usage_display_fields(UpsertUsageRecord {
+            request_id: "req-1".to_string(),
+            user_id: Some("user-1".to_string()),
+            api_key_id: Some("key-1".to_string()),
+            username: Some("alice".to_string()),
+            api_key_name: Some("default".to_string()),
+            provider_name: "OpenAI".to_string(),
+            model: "gpt-5".to_string(),
+            target_model: None,
+            provider_id: None,
+            provider_endpoint_id: None,
+            provider_api_key_id: None,
+            request_type: Some("chat".to_string()),
+            api_format: Some("openai:chat".to_string()),
+            api_family: Some("openai".to_string()),
+            endpoint_kind: Some("chat".to_string()),
+            endpoint_api_format: Some("openai:chat".to_string()),
+            provider_api_family: Some("openai".to_string()),
+            provider_endpoint_kind: Some("chat".to_string()),
+            has_format_conversion: Some(false),
+            is_stream: Some(false),
+            input_tokens: Some(10),
+            output_tokens: Some(20),
+            total_tokens: Some(30),
+            cache_creation_input_tokens: None,
+            cache_creation_ephemeral_5m_input_tokens: None,
+            cache_creation_ephemeral_1h_input_tokens: None,
+            cache_read_input_tokens: None,
+            cache_creation_cost_usd: None,
+            cache_read_cost_usd: None,
+            output_price_per_1m: None,
+            total_cost_usd: Some(0.25),
+            actual_total_cost_usd: Some(0.15),
+            status_code: Some(200),
+            error_message: None,
+            error_category: None,
+            response_time_ms: Some(120),
+            first_byte_time_ms: Some(40),
+            status: "completed".to_string(),
+            billing_status: "pending".to_string(),
+            request_headers: None,
+            request_body: None,
+            request_body_ref: None,
+            provider_request_headers: None,
+            provider_request_body: None,
+            provider_request_body_ref: None,
+            response_headers: None,
+            response_body: None,
+            response_body_ref: None,
+            client_response_headers: None,
+            client_response_body: None,
+            client_response_body_ref: None,
+            candidate_id: None,
+            candidate_index: None,
+            key_name: None,
+            planner_kind: None,
+            route_family: None,
+            route_kind: None,
+            execution_path: None,
+            local_execution_runtime_miss_reason: None,
+            request_metadata: None,
+            finalized_at_unix_secs: None,
+            created_at_unix_ms: Some(100),
+            updated_at_unix_secs: 101,
+        });
+
+        assert_eq!(usage.user_id.as_deref(), Some("user-1"));
+        assert_eq!(usage.api_key_id.as_deref(), Some("key-1"));
+        assert_eq!(usage.username, None);
+        assert_eq!(usage.api_key_name, None);
+        assert_eq!(usage.provider_name, "OpenAI");
+        assert_eq!(usage.model, "gpt-5");
+    }
+}