Set idle timeout when streaming responses

[mworrell]

Also upgrade cowboy, cowlib and zotonic_stdlib.
Add the lock file.

[Copilot]

Pull Request Overview

This PR adds idle timeout management for streaming responses in cowmachine. The purpose is to prevent timeouts during streaming operations while maintaining appropriate timeout settings when not streaming.

• Adds a configurable idle timeout mechanism for HTTP streaming responses
• Sets idle timeout to infinity during streaming operations and restores it to 60 seconds afterward
• Removes some commented-out code and upgrades dependencies

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[Copilot]

Pull Request Overview

Copilot reviewed 4 out of 7 changed files in this pull request and generated 2 comments.

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