chore(routes): delete dev-only demo route

Removes scaffolding pages from initial Paraglide setup that were never
navigated to in production. Shrinks the measured coverage surface and
removes dead code from the production bundle. CLAUDE.md route tables
updated to drop the demo/ entry.

Refs #496.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

CLAUDE.md

@@ -202,8 +202,7 @@ frontend/src/routes/
 ├── profile/                User profile settings
 ├── users/[id]/             Public user profile page
 ├── login/ logout/ register/
-├── forgot-password/ reset-password/
-└── demo/                   Dev-only demos
+└── forgot-password/ reset-password/
 ```
 
 ### API Client Pattern