Bootstrap OpenAPI for Phoenix

Set up OpenAPI documentation with authentication and authorization in a Phoenix project using open_api_spex. This includes:

• OpenAPI 3.0 specification with Swagger UI
• User authentication via phx.gen.auth
• Multi-tenant accounts with User many-to-many relationship
• API key authentication (pk_/sk_ tokens) scoped to user+account
• Read/write access control
• CORS configuration
• TypeScript type generation support

Prerequisites: This command assumes you have an existing Phoenix project. If not, run /bootstrap-phoenix first.

Phase 1: Generate User Authentication

1.1 Run phx.gen.auth