feat: allow command timeouts in config

[OfriHarlev]

Summary

• add a nested timeouts config section to proofshot.config.json
• make browser open, recording, exec passthrough, screenshot, and video trim timeouts configurable
• add focused tests for nested timeout config merging
• document the timeout configuration in the user-facing docs

Problem

ProofShot currently hardcodes several operational timeouts.

That works well in fast local environments, but it makes slower projects and CI-like setups harder to support without source patches.

Solution

This change adds a project-level timeouts section so browser open, recording, screenshot, exec passthrough, and video trim behavior can be tuned without modifying ProofShot source.

Testing

• npm test
• npm run build

[OfriHarlev]

@AmElmo I rebased this PR with latest main

[OfriHarlev]

@AmElmo any chance this can get a review?