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。

frontend/src/api/endpoints/keys.ts

@@ -4,6 +4,10 @@ import type { EndpointAPIKey, AllowedModels } from './types'
 // Re-export types for convenience
 export type { EndpointAPIKey, AllowedModels }
 
+interface KeyRequestOptions {
+  timeout?: number
+}
+
 /**
  * 能力定义类型
  */
@@ -179,9 +183,14 @@ export async function updateProviderKey(
     model_include_patterns: string[]  // 模型包含规则
     model_exclude_patterns: string[]  // 模型排除规则
     proxy: import('./types').ProxyConfig | null  // Key 级别代理配置
-  }>
+  }>,
+  requestOptions?: KeyRequestOptions,
 ): Promise<EndpointAPIKey> {
-  const response = await client.put(`/api/admin/endpoints/keys/${keyId}`, data)
+  const response = await client.put(
+    `/api/admin/endpoints/keys/${keyId}`,
+    data,
+    requestOptions,
+  )
   return response.data
 }
 

frontend/src/api/endpoints/providers.ts

@@ -8,6 +8,10 @@ import type {
   ProxyConfig,
 } from './types'
 
+interface ProviderRequestOptions {
+  timeout?: number
+}
+
 /**
  * 获取 Providers 摘要（分页）
  */
@@ -73,9 +77,10 @@ export async function updateProvider(
     claude_code_advanced: ClaudeCodeAdvancedConfig | null
     pool_advanced: PoolAdvancedConfig | null
     failover_rules: FailoverRulesConfig | null
-  }>
+  }>,
+  requestOptions?: ProviderRequestOptions,
 ): Promise<ProviderWithEndpointsSummary> {
-  const response = await client.patch(`/api/admin/providers/${providerId}`, data)
+  const response = await client.patch(`/api/admin/providers/${providerId}`, data, requestOptions)
   return response.data
 }