fix(server): add 10s timeout to TLS handshake

[persimmon16]

Summary

• Wraps the TLS accept() call with a 10-second tokio::time::timeout to prevent slowloris-style attacks
• Connections that fail to complete the TLS handshake within 10s are dropped with a debug log

Related Issue

Production readiness audit finding (P1): no timeout on TLS handshake — a malicious client could hold a connection open indefinitely.

Changes

• crates/openshell-server/src/lib.rs: Wrapped tls_acceptor.inner().accept(stream) with tokio::time::timeout(Duration::from_secs(10), ...)

Testing

• cargo check -p openshell-server passes
• 10s is generous for legitimate clients while preventing indefinite hangs

Checklist

• Conventional commit format
• No secrets committed
• Scoped to the issue at hand

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[github-actions]

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