refactor: 拆分 gateway 单体为独立 crate，新增 systemd 部署方案

将 gateway 内部的 model-fetch、provider-transport、scheduler-core、
usage-runtime、video-tasks-core 模块提取为独立 crate；重构 gateway
内部模块结构（state/router/cache/data/query 等）；移除大量遗留模块
文件；新增 systemd 二进制部署骨架及相关文档；更新前端 usage 相关
API 和组件。

crates/aether-usage-runtime/src/record.rs

@@ -0,0 +1,116 @@
+use aether_data::repository::usage::UpsertUsageRecord;
+use aether_data::DataLayerError;
+
+use crate::{UsageEvent, UsageEventType};
+
+pub fn build_upsert_usage_record_from_event(
+    event: &UsageEvent,
+) -> Result<UpsertUsageRecord, DataLayerError> {
+    let (status, billing_status) = lifecycle_status_and_billing(event.event_type);
+    let data = event.data.clone();
+    let now_unix_secs = event.timestamp_ms / 1_000;
+
+    Ok(UpsertUsageRecord {
+        request_id: event.request_id.clone(),
+        user_id: data.user_id,
+        api_key_id: data.api_key_id,
+        username: data.username,
+        api_key_name: data.api_key_name,
+        provider_name: data.provider_name,
+        model: data.model,
+        target_model: data.target_model,
+        provider_id: empty_to_none(data.provider_id),
+        provider_endpoint_id: empty_to_none(data.provider_endpoint_id),
+        provider_api_key_id: empty_to_none(data.provider_api_key_id),
+        request_type: data.request_type,
+        api_format: data.api_format,
+        api_family: data.api_family,
+        endpoint_kind: data.endpoint_kind,
+        endpoint_api_format: data.endpoint_api_format,
+        provider_api_family: data.provider_api_family,
+        provider_endpoint_kind: data.provider_endpoint_kind,
+        has_format_conversion: data.has_format_conversion,
+        is_stream: data.is_stream,
+        input_tokens: data.input_tokens,
+        output_tokens: data.output_tokens,
+        total_tokens: data.total_tokens,
+        cache_creation_input_tokens: data.cache_creation_input_tokens,
+        cache_read_input_tokens: data.cache_read_input_tokens,
+        cache_creation_cost_usd: data.cache_creation_cost_usd,
+        cache_read_cost_usd: data.cache_read_cost_usd,
+        output_price_per_1m: data.output_price_per_1m,
+        total_cost_usd: data.total_cost_usd,
+        actual_total_cost_usd: data.actual_total_cost_usd,
+        status_code: data.status_code,
+        error_message: data.error_message,
+        error_category: data.error_category,
+        response_time_ms: data.response_time_ms,
+        first_byte_time_ms: data.first_byte_time_ms,
+        status: status.to_string(),
+        billing_status: billing_status.to_string(),
+        request_headers: data.request_headers,
+        request_body: data.request_body,
+        provider_request_headers: data.provider_request_headers,
+        provider_request_body: data.provider_request_body,
+        response_headers: data.response_headers,
+        response_body: data.response_body,
+        client_response_headers: data.client_response_headers,
+        client_response_body: data.client_response_body,
+        request_metadata: data.request_metadata,
+        finalized_at_unix_secs: Some(now_unix_secs),
+        created_at_unix_secs: Some(now_unix_secs),
+        updated_at_unix_secs: now_unix_secs,
+    })
+}
+
+fn lifecycle_status_and_billing(event_type: UsageEventType) -> (&'static str, &'static str) {
+    match event_type {
+        UsageEventType::Pending => ("pending", "pending"),
+        UsageEventType::Streaming => ("streaming", "pending"),
+        UsageEventType::Completed => ("completed", "pending"),
+        UsageEventType::Failed => ("failed", "void"),
+        UsageEventType::Cancelled => ("cancelled", "void"),
+    }
+}
+
+fn empty_to_none(value: Option<String>) -> Option<String> {
+    value
+        .map(|value| value.trim().to_string())
+        .filter(|value| !value.is_empty())
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::{UsageEvent, UsageEventData, UsageEventType};
+
+    use super::build_upsert_usage_record_from_event;
+
+    #[test]
+    fn builds_upsert_record_from_terminal_event() {
+        let record = build_upsert_usage_record_from_event(&UsageEvent {
+            event_type: UsageEventType::Completed,
+            request_id: "req-1".to_string(),
+            timestamp_ms: 1_700_000_000_000,
+            data: UsageEventData {
+                user_id: Some("user-1".to_string()),
+                api_key_id: Some("key-1".to_string()),
+                provider_name: "OpenAI".to_string(),
+                model: "gpt-5".to_string(),
+                api_format: Some("openai:chat".to_string()),
+                endpoint_api_format: Some("openai:chat".to_string()),
+                input_tokens: Some(10),
+                output_tokens: Some(20),
+                total_tokens: Some(30),
+                status_code: Some(200),
+                ..UsageEventData::default()
+            },
+        })
+        .expect("record should build");
+
+        assert_eq!(record.request_id, "req-1");
+        assert_eq!(record.status, "completed");
+        assert_eq!(record.billing_status, "pending");
+        assert_eq!(record.total_tokens, Some(30));
+        assert_eq!(record.finalized_at_unix_secs, Some(1_700_000_000));
+    }
+}