Presentation success screen

### Description
Implement the **Presentation Success** screen (`/presentation/success`) — design screen `Desktop-14`.

### UI spec
- Full-screen layout, no header bar
- Center-aligned illustration: hand holding a card with a green checkmark
- Text: `"Information sent successfully"`
- Single primary button at the bottom: **"Go back home"** (green)

### Acceptance criteria
- [ ] Screen is only reachable after a successful `presentCredential()` stub call
- [ ] Tapping **"Go back home"** navigates to `/` and clears all presentation flow state
- [ ] Direct navigation to `/presentation/success` without completing the flow redirects to `/`
- [ ] The illustration is an SVG or existing asset — no external image dependency

### Notes
OID4VP spec ref: §8.2 (Response Mode `direct_post`).