feat: add Novita AI as model provider

[jasonhp]

新增渠道：Novita AI

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）

[codecov]

Codecov Report

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

Project coverage is 1.09%. Comparing base (273be55) to head (0b9dfa7).
Report is 5 commits behind head on main.

Files	Patch %	Lines
relay/adaptor/novita/main.go	0.00%	4 Missing ⚠️
relay/adaptor/openai/adaptor.go	0.00%	2 Missing ⚠️
relay/adaptor/openai/compatible.go	0.00%	2 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##            main   #1609      +/-   ##
========================================
- Coverage   1.09%   1.09%   -0.01%     
========================================
  Files        130     131       +1     
  Lines       9698    9710      +12     
========================================
  Hits         106     106              
- Misses      9578    9590      +12     
  Partials      14      14              

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