Add rc:smoke smoke-test script and switch integration test to native crypto

[DanFashauer]

Motivation

• Add an automated smoke test to verify local server health, public API v1 behavior, webhook signing, and demo media generation.
• Provide a reusable script for CI or local validation that can start the dev server if needed and run end-to-end checks.
• Modernize the integration test to use the native crypto import instead of a runtime require call.

Description

• Added scripts/rc-smoke.ts, a Bun-compatible smoke test that checks /api/health, /api/demo/verify scenarios, /api/v1 endpoints (including auth checks), session start signature handling (missing, malformed, and valid), and verifies demo media artifacts are produced; the script can start and stop the local dev server as needed.
• Added an npm script entry rc:smoke in package.json to run the new smoke test via bun.
• Updated tests/api/integration-v1.test.ts to import crypto using import crypto from 'node:crypto' and removed the dynamic require usage used for HMAC signing.

Testing

• Ran the Vitest integration suite using vitest to validate API tests after the change and observed successful execution of the modified test file.
• Executed the smoke script locally with bun run rc:smoke to validate end-to-end checks including server startup, endpoints, signature verification, and demo media generation, and it completed successfully.

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Codex Task