* Add CI workflow and apply ruff formatting
* Disable cdk synth — email_processor uses pre-built package dir
The email_processor Lambda bundles deps into a gitignored package/
directory. cdk synth fails in CI without a build step to recreate it.
Disabling until packaging is standardized.
* Use CDK BundlingOptions for email_processor Lambda packaging
Replaces the pre-built gitignored package/ directory with CDK's
built-in bundling. Deps are now installed inside a Docker container
during cdk synth, so the build works identically locally and in CI.
Re-enables run-cdk-synth in the CI workflow.
