GitLab

- 渠道模型映射：支持精确匹配和通配符映射，按平台隔离
- 渠道模型定价：支持 token/按次/图片三种计费模式，区间分层定价
- 模型限制：渠道可限制仅允许定价列表中的模型
- 计费模型来源：支持 requested/upstream 两种计费模型选择
- 用量统计：usage_logs 新增 channel_id/model_mapping_chain/billing_tier/billing_mode 字段
- Dashboard 支持 model_source 维度（requested/upstream/mapping）查看模型统计
- 全部 gateway handler 统一接入 ResolveChannelMappingAndRestrict
- 修复测试：同步 SoraGenerationRepository 接口、SQL INSERT 参数、scan 字段

Show upstream model mapping (requested -> upstream) in UsageTable with arrow notation. Add requested/upstream/mapping source toggle to ModelDistributionChart with lazy loading — only fetches data when user switches tab, with per-source cache invalidation on filter changes. Include upstream_model column in Excel export and i18n for en/zh.

Click on a group name, model name, or endpoint name in the distribution
tables to expand and show per-user usage breakdown (requests, tokens,
actual cost, standard cost).

Backend: new GET /admin/dashboard/user-breakdown API with group_id,
model, endpoint, endpoint_type filters.
Frontend: clickable rows with expand/collapse sub-table in all three
distribution charts.

- 统一移除语句末尾分号，规范代码格式
- 优化组件类型定义和 props 声明
- 改进组件文档和示例代码
- 提升代码可读性和一致性