UI #23 — Add QR code share for transactions and accounts

[Tinna23]

Description

Mobile users often want to share a transaction or account with someone nearby. A QR code share button generates a scannable code for the current result URL.

What To Build

src/components/common/QRShareButton.tsx

• Add qrcode.react as a dependency
• Props: url: string, label?: string
• Renders a 'Share QR' button
• Clicking opens a modal showing the QR code (256×256)
• Below QR: full URL in monospace + Copy URL button
• Modal: close button + backdrop click + Escape key to dismiss
• Mobile: bottom-sheet style. Desktop: centred modal

Add to:

• Transaction result — URL is the app page with the hash pre-filled
• Account result — URL is the app page with the address pre-filled

Key Files

• src/components/common/QRShareButton.tsx
• src/components/TransactionResult.tsx
• src/components/AccountResult.tsx
• package.json (add qrcode.react)

Acceptance Criteria

• QR code renders correctly for both transaction and account results
• Scanning the QR on mobile opens the correct page
• Copy URL button works with toast feedback
• Modal closes on backdrop click and Escape
• Bottom-sheet on mobile, centred modal on desktop

Complexity: Medium · 150 pts
Stage: S9 — Shareability (Wave 2)
Depends on: UI #6, UI #7