[CLI] Create cg generate server command

[widal001]

Generating server code

User story

As a developer implementing a CommonGrants API, I want to run a command that auto-generates an API server interface from a specification, so that I can follow a pattern of specification-driven development and quickly build APIs from scratch using the CommonGrants library.

Developer experience

cg generate server <path-to-typespec>

Additional Features

• Allow specifying a language/framework with --lang (e.g., Python, Node.js).
• Enable plugin support for custom server code generation.
• Generate only specific components with --only <controllers|models|routes>.

Example Usage

# Generate a server using the default framework
cg generate server grants-api.tsp

# Generate a server for a specific language or framework
cg generate server grants-api.tsp --lang python

# Generate only controllers and routes
cg generate server grants-api.tsp --only controllers,routes

Technical details

• This may require a combination of TypeSpec emitters and OpenAPI codegen.
• If an API framework isn't specified by the user via a flag, the CLI should prompt a user to choose one.
• Ideally, this entry point would be designed to support plugins for custom server code generators.

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