feat: provider api_formats 可空继承、OpenAI 图片 edit/variation 与用量配额多项补强

- 鉴权: provider_api_keys.api_formats 改为可空，OAuth 托管 key 自动继承 provider endpoints 激活格式，相关 handler/测试同步更新
- 图片 planner: OpenAI 图片路由新增 edit/variation 操作并完善参数校验、响应合并与流式处理
- 用量: user me usage 返回区分 client_requested_stream/upstream_is_stream，前端 usage 列表筛选与展示增强
- 统计: stats_daily_model 新增 cache_creation_ephemeral_5m/1h tokens 字段与回填链路
- 配额/observability: quota repository 新增内存与 SQL 扩展，admin observability usage 字段扩充
- 其它: OAuth 导入/轮询收敛、provider 汇总与 pool admin 读写链路小修、新增 system_config 缓存与 provider template handler

Closes #318

Co-authored-by: Entropy.Xu <53283266+Entropy-Xu@users.noreply.github.com>

frontend/src/api/dashboard.ts

@@ -167,6 +167,9 @@ export interface RequestDetail {
   price_per_request?: number  // 按次计费价格
   request_type: string
   is_stream: boolean
+  upstream_is_stream?: boolean
+  client_requested_stream?: boolean
+  client_is_stream?: boolean
   status_code: number
   status?: string  // pending, streaming, completed, failed, cancelled
   error_message?: string

frontend/src/api/me.ts

@@ -61,6 +61,9 @@ export interface UsageRecordDetail {
   rate_multiplier?: number  // 成本倍率（仅管理员可见）
   response_time_ms?: number
   is_stream: boolean
+  upstream_is_stream?: boolean
+  client_requested_stream?: boolean
+  client_is_stream?: boolean
   created_at: string
   cache_creation_input_tokens?: number
   cache_creation_ephemeral_5m_input_tokens?: number
@@ -301,6 +304,10 @@ export const meApi = {
       first_byte_time_ms: number | null
       api_format?: string | null
       endpoint_api_format?: string | null
+      is_stream?: boolean | null
+      upstream_is_stream?: boolean | null
+      client_requested_stream?: boolean | null
+      client_is_stream?: boolean | null
       has_format_conversion?: boolean | null
       has_fallback?: boolean | null
       target_model?: string | null

frontend/src/api/usage.ts

@@ -312,6 +312,10 @@ export const usageApi = {
       provider_key_name?: string | null
       api_format?: string | null
       endpoint_api_format?: string | null
+      is_stream?: boolean | null
+      upstream_is_stream?: boolean | null
+      client_requested_stream?: boolean | null
+      client_is_stream?: boolean | null
       has_format_conversion?: boolean | null
       has_fallback?: boolean | null
       target_model?: string | null