[Fix] DeepSeek V4 costs are underestimated after pricing changes (#1237)

* feat(providers): add DeepSeek V4 Pro 0813

* fix(providers): distinguish DeepSeek V4 checkpoints

* fix(providers): update DeepSeek V4 pricing

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Co-authored-by: @taltas <6816042+taltas@users.noreply.github.com>