remove zstd encoding

[joshrmcdaniel]

ZSTD isn't supported in the reqwest version used

[zeropath-ai]

✅ No security or compliance issues detected. Reviewed everything up to acf98fc.

Security Overview

• 🔎 Scanned files: 1 changed file(s)
• 🔗 Scan Link: https://zeropath.com/app/issues?scanId=325d35bf-cab6-4fe1-9e00-769a64019ea3

Detected Code Changes

Change Type	Relevant files
Enhancement	► serve.rs     Add handling for zstd encoding in request headers

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