Can I build my own WeTransfer with AI?

Build a simple file transfer app similar to WeTransfer for sending large files via a shareable link.

**Objective:** Let users upload a file and share a download link with optional expiry.

**Target user:** A freelancer or small team that wants a branded file-drop page without WeTransfer Pro fees.

**Core functionality:**
- Drag-and-drop upload page
- Generate unique download URL after upload completes
- Set expiry (e.g. 7 days) and optional recipient email
- Download page that serves the file until expiry

**Pages/screens:**
- Upload page (public)
- Success page with copyable link
- Download page (public, via token in URL)

**Data model:**
- Transfer: { id, token, filename, size, storageKey, expiresAt, createdAt, recipientEmail? }

**Authentication:** Optional admin dashboard to see active transfers.

**APIs/integrations:** Object storage (S3-compatible). Email optional for MVP.

**Explicit exclusions:** No resumable multipart uploads, no password protection, no custom backgrounds, no analytics in v1.