Add automated tests and CI for unity voice workflow

[G-Fourteen]

Summary

• add a GitHub Actions workflow that installs dependencies for the web client and voice bridge and runs the vitest suite
• update the Twilio voice server helpers to expose test hooks and call the Pollinations gateway with the unity model
• configure project-level test tooling and add a comprehensive vitest suite covering voice bridge utilities and routes

Testing

• npm test

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https://chatgpt.com/codex/tasks/task_b_68c96fe1ddb88329b8f6cfdb5ed87105