Scaffolded sample `hello` module emits SM019 warning on every boot

[antosubash]

Summary

A fresh smpy new myapp --yes includes a sample hello module under modules/hello/. Every boot logs:

⚠ SM019 [WARNING] Hello: Module 'Hello' registers view routes (view_prefix='/hello') but no menu items or permissions
  ↳ Suggestion: Override register_menu_items() to surface this module in the sidebar, register_permissions() to surface it in the role editor, or clear view_prefix if it's API-only

Results: 0 error(s), 1 warning(s), 0 info

…and confirming this, GET /hello returns 404 because no view is wired up — only /api/hello/ works.

A user's first boot of their scaffold shouldn't produce diagnostic warnings. It teaches the wrong lesson: "warnings are normal noise, ignore them."

Suggested fix (pick one)

1. Sample module should be self-consistent. Either drop view_prefix='/hello' from the template (it becomes an API-only sample), or add a minimal register_menu_items + a stub pages/Browse.tsx so /hello actually renders.
2. Tighten the template's defaults. hello/module.py should ship without view_prefix and let smpy create-module add it when the user opts in.

(1.a) — drop view_prefix — is the smallest change.