chore: prepare the demo for public release (license, tests, CI)

[thierrypdamiba]

Summary

Gets the Cisco Duo x Arcade demo ready to go public alongside the blog. Adds an MIT license, an offline smoke-test suite, CI, and tidies the README. No changes to the demo's app code.

What's in here

• MIT LICENSE (matches arcade-mcp)
• crm_api smoke tests covering the per-tool 403 (Layer 1) and the step-up approve/deny paths (Layer 2), all offline in dev mode
• GitHub Actions CI that runs those tests on push and PR
• README cleanup: dropped the leftover "Create the repo" snippet, added License and Tests sections

Testing

cd crm_api
uv venv .venv && uv pip install --python .venv/bin/python -r requirements-dev.txt
.venv/bin/pytest   # 7 passed

Live Duo sign-in and arcade deploy aren't exercised here (they need a Duo and Arcade account); the repo's screenshots show the real end-to-end run.