Convert, PWA install, and the claim-link story on the landing

Day three of the network pivot.

- Convert: AVNU private swaps as a consumer sheet — debounced live quotes,
  rate + USD value, in-pool honesty copy; reachable from the balance card
  and the menu; SWAP ledger entries with the executor->AMM observer string
- PWA: manifest + maskable icon set (SVG source rasterized to 512/192/180),
  standalone display, /app start_url, apple-touch metadata — Add to Home
  Screen now installs Lumen like an app
- Landing: claim links promoted to feature 01 with their own artifact
  (link -> claim card), rows renumbered and re-alternated; hero copy names
  the wallet-optional promise
- README rewritten around the network (links as the product, escrow
  contract detail, both test suites); .env.example documents the escrow
  address flag

172 TS + 50 Cairo tests green; build ships all routes.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>