Redesign swap interface

[henghonglee]

Summary

• Introduce a warm, trust-forward design system with cream/walnut color palette, DM Sans typography, and custom Tailwind design tokens (colors, border-radius, animations)
• Create reusable UI primitives (Card, Button, AmountInput, AssetPill, AssetSheet) in src/ui/ and a unified ReceiveAddressField with clipboard paste and wallet auto-fill
• Replace chain tab bar with a bottom-sheet asset selector modal, move Solana wallet providers to App.tsx for cross-chain availability, and restyle the Order status view

Test plan

• Verify each chain selection (Polygon/Solana/Tron) works via the asset sheet
• Confirm amount input accepts valid numbers and the asset pill displays correct token + chain logos
• Test receive address auto-fill for Polygon (Web3Modal) and Solana (WalletAdapter)
• Test manual address entry and paste button for Tron
• Verify order creation flow end-to-end (create order → Lightning QR → escrow → release)
• Check responsive layout on mobile and desktop viewports
• Confirm the new design tokens render correctly (cream background, walnut buttons, DM Sans font)

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