feat: add standalone wallet PWA build

Adds a standalone Lightning wallet PWA at wallet.${domain}, built
from the existing src/modules/wallet plugin. Mirrors the Castle and
Activities standalone patterns:
- wallet.html entry, vite.wallet.config.ts (outDir: dist-wallet,
  manifest id: wallet-app, theme: yellow #eab308 — Manipura chakra)
- src/wallet-app/{main.ts, app.ts, app.config.ts, App.vue} bootstraps
  base + wallet only, with acceptTokenFromUrl for shared auth from hub
- npm run dev:wallet / build:wallet / preview:wallet
- main app SW denylist extended with /wallet/

Closes #19.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

vite.config.ts

@@ -25,7 +25,7 @@ export default defineConfig(({ mode }) => ({
           '**/*.{js,css,html,ico,png,svg}'
         ],
         // Don't intercept standalone app paths — they have their own service workers
-        navigateFallbackDenylist: [/^\/sortir\//, /^\/castle\//],
+        navigateFallbackDenylist: [/^\/sortir\//, /^\/castle\//, /^\/wallet\//],
       },
       includeAssets: [
         'favicon.ico',