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).

src/i18n/en-US/index.ts

@@ -0,0 +1,7 @@
+// This is just an example,
+// so you can safely delete all default props below
+
+export default {
+  failed: 'Action failed',
+  success: 'Action was successful',
+};

src/i18n/index.ts

@@ -0,0 +1,5 @@
+import enUS from './en-US';
+
+export default {
+  'en-US': enUS,
+};