NavIcon ships only ~10 hardcoded icons; common module icons render as empty squares #92

Summary

@simple-module-py/ui/components/NavIcon.tsx ships a hardcoded Record<string, React.ReactNode> with about 10 SVG icons (home, package, users, user, settings, shield, activity, files, layers, shield-check, log-out). When a module's register_menu_items declares an icon outside this set, NavIcon falls through to <span className="w-5 h-5" /> and the sidebar shows an empty placeholder where the icon should be.

Repro

The framework's own modules already request icons that don't exist in the map:

• feature_flags/constants.py:24 → MENU_ICON = "flag" → no glyph
• bell (commonly used by notification modules) → no glyph
• bar-chart-3 (commonly used by report modules) → no glyph

App-level modules can't add new icons without forking NavIcon.tsx.

Expected

Either:

1. The map covers a broader set of common lucide-react icon names, or
2. NavIcon defers to lucide-react when the name isn't in the local map (icons-by-name lookup), or
3. There's a documented host-level extension point for registering additional icons.

Workaround

In a downstream app I added a Vite resolve plugin that intercepts both the bare specifier @simple-module-py/ui/components/NavIcon and the relative ../components/NavIcon (the form SidebarLayout.tsx uses internally) to redirect to a local NavIcon.tsx with extra icons. `resolve.alias` on the bare specifier alone wasn't enough because SidebarLayout reaches for the relative path.

Acceptance

• Built-in modules render with visible icons in the sidebar without app-level patching.
• App-level modules can declare arbitrary lucide names without falling through to the empty placeholder.