sattle: Quasar PWA scaffold with lnurlcash-kit protocol core

M1: Quasar 2 / Vue 3 / TS / Pinia / i18n / PWA app shell in the lnurl-wallet
palette (#002222/#004444/#55ffcc, Noto Sans). Protocol layer is the external
lnurlcash-kit library (git dependency on the fork until upstream merges the
prepare fix / publishes to npm); keys.ts + receive.ts vendored from
lnurl-wallet with the derivation domain renamed to 'sattle'. Nix dev shell,
ci workflow (typecheck, vitest, pwa build).

.editorconfig

@@ -0,0 +1,7 @@
+[*.{js,jsx,mjs,cjs,ts,tsx,mts,cts,vue}]
+charset = utf-8
+indent_size = 2
+indent_style = space
+end_of_line = lf
+insert_final_newline = true
+trim_trailing_whitespace = true