Refactor Plan Generator (Multi-File)

I want to refactor [DESCRIPTION OF REFACTOR - e.g., extract auth logic into its own service].

Before touching any code, produce a refactor plan:
1. List the files that will be modified, created, or deleted.
2. Show the new architecture in a one-paragraph summary.
3. Identify the riskiest steps and how to mitigate them.
4. Propose a safe ordering: which step lands first, second, etc., so the codebase stays green at every step.
5. List tests to add or update.

No code yet. Plan only. I'll review and then we execute one step at a time.