Break a build into steps that each run

Break what I am building into small steps.

Rules:
1. ***Something has to work at the end of every step.*** **No step that produces a screen with nothing behind it.**
2. Step 1 is the simplest possible form. One feature, one screen.
3. Per step:
   - What now works
   - **How to check it**
   - The request to send the AI (**copy-pasteable**)
4. **If a step is too big, split it.** Too big means it will not finish in one request.
5. ***Put the hard-to-reverse decisions early*** (data structure, authentication).
6. Keep a separate list of what comes later and what can be skipped.
7. **Mark the steps likely to stall me at my level given below**.