[docs] added torch.compile cache to dpsk manual

[FrankLeeeee]

Motivation

Some users are not familiar with how caching works for torch.compile as stated in #3614.

Modifications

Add a section in DeepSeek documentation on how to manage the caching for torch.compile.

Checklist

• Format your code according to the Code Formatting with Pre-Commit.
• Add unit tests as outlined in the Running Unit Tests.
• Update documentation / docstrings / example tutorials as needed, according to Writing Documentation.
• Provide throughput / latency benchmark results and accuracy evaluation results as needed, according to Benchmark and Profiling and Accuracy Results.
• For reviewers: If you haven't made any contributions to this PR and are only assisting with merging the main branch, please remove yourself as a co-author when merging the PR.
• Please feel free to join our Slack channel at https://slack.sglang.ai to discuss your PR.

[FrankLeeeee]

cc @zhaochenyang20 @zhyncs @shuaills for #3614