page/settings-page: build user settings page

[Rend1027]

• Create a new route/page: /settings
• Create a SettingsPage component that:
  - [ ] Displays a heading ("Your Settings")
  - [ ] Includes the visibility toggle
• Add a back/home feature for easy navigation
• Add success message or toast on save (e.g., “Settings updated”)

Having a dedicated Settings page gives users control over how their presence is shown in the app, starting with public/private visibility — and it gives your frontend team a structured place to expand later.