Change namespace to DeepSeekPhp

[hishamco]

According to https://www.deepseek.com/ & https://en.wikipedia.org/wiki/DeepSeek we should use DeepSeek instead of Deepseek

Much better to use DeepSeek as namespace instead of DeepseekPhp

[omaralalwi]

@hishamco
please write clear changes in changelos file https://github.com/deepseek-php/deepseek-php-client/blob/master/CHANGELOG.md

these changes should released in new version , new version will be 2.0.0

[hishamco]

if DeepSeek as a namespace makes sense, I will write a change log. BTW upcoming version shouldn't necessarily to be 2.0.0 unless there are a major breaking changes

[hishamco]

It seems you didn't check my last comment to use DeepSeek instead