feat: support gpt-4o mini

[HynoR]

resolve issue: #1664

ps: 有一个小坑， 4o mini 识图模型的tile价格对标 4o，为mini的token价格的33倍。因此我修改了图片token计算方式
ref: additionalCost

我已确认该 PR 已自测通过，相关截图如下：
（此处放上测试通过的截图，如果不涉及前端改动或从 UI 上无法看出，请放终端启动成功的截图）

[WqyJh]

官网上的价格计算器上显示，gpt-4o mini的图像价格确实与 gpt-4o 一致

[HynoR]

总之改动了一下图片计算token的函数避免错误消耗非流模式下的token，希望帮忙review。也请使用该模型的朋友注意一下这个特殊的模型计算方法。

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 8 lines in your changes missing coverage. Please review.

Project coverage is 1.29%. Comparing base (2a892c1) to head (d04c0dc).

Files	Patch %	Lines
relay/adaptor/openai/token.go	0.00%	6 Missing ⚠️
relay/billing/ratio/model.go	0.00%	2 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##            main   #1665      +/-   ##
========================================
- Coverage   1.29%   1.29%   -0.01%     
========================================
  Files        142     142              
  Lines      10070   10076       +6     
========================================
  Hits         130     130              
- Misses      9926    9932       +6     
  Partials      14      14              

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