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>

package.json

@@ -15,6 +15,9 @@
     "dev:castle": "vite --host --config vite.castle.config.ts",
     "build:castle": "vue-tsc -b && vite build --config vite.castle.config.ts",
     "preview:castle": "vite preview --host --config vite.castle.config.ts",
+    "dev:wallet": "vite --host --config vite.wallet.config.ts",
+    "build:wallet": "vue-tsc -b && vite build --config vite.wallet.config.ts",
+    "preview:wallet": "vite preview --host --config vite.wallet.config.ts",
     "electron:dev": "concurrently \"vite --host\" \"electron-forge start\"",
     "electron:build": "vue-tsc -b && vite build && electron-builder",
     "electron:package": "electron-builder",