feat: add standalone chat PWA build

Adds a standalone encrypted chat PWA at chat.${domain}, built from
the existing src/modules/chat plugin. Same standalone pattern as
wallet/castle/activities:
- chat.html entry, vite.chat.config.ts (outDir: dist-chat,
  manifest id: chat-app, theme: green #16a34a — Anahata chakra)
- src/chat-app/{main.ts, app.ts, app.config.ts, App.vue} bootstraps
  base + chat only, with acceptTokenFromUrl for shared auth from hub
- npm run dev:chat / build:chat / preview:chat
- main app SW denylist extended with /chat/

Closes #20.

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

vite.chat.config.ts

@@ -0,0 +1,115 @@
+import { fileURLToPath, URL } from 'node:url'
+import vue from '@vitejs/plugin-vue'
+import tailwindcss from '@tailwindcss/vite'
+import { defineConfig, type Plugin } from 'vite'
+import { VitePWA } from 'vite-plugin-pwa'
+import { ViteImageOptimizer } from 'vite-plugin-image-optimizer'
+import { visualizer } from 'rollup-plugin-visualizer'
+
+function chatHtmlPlugin(): Plugin {
+  return {
+    name: 'chat-html-rewrite',
+    configureServer(server) {
+      server.middlewares.use((req, _res, next) => {
+        if (
+          req.url &&
+          !req.url.startsWith('/@') &&
+          !req.url.startsWith('/src/') &&
+          !req.url.startsWith('/node_modules/') &&
+          !req.url.includes('.')
+        ) {
+          req.url = '/chat.html'
+        }
+        next()
+      })
+    },
+  }
+}
+
+/**
+ * Vite config for the standalone Chat app.
+ *
+ * Set VITE_BASE_PATH to deploy under a path prefix:
+ *   VITE_BASE_PATH=/chat/ → app.${domain}/chat/ (shared auth)
+ *   (default: /)          → chat.${domain} (standalone subdomain)
+ */
+export default defineConfig(({ mode }) => ({
+  base: process.env.VITE_BASE_PATH || '/',
+  plugins: [
+    chatHtmlPlugin(),
+    vue(),
+    tailwindcss(),
+    VitePWA({
+      registerType: 'autoUpdate',
+      devOptions: { enabled: true },
+      workbox: {
+        globPatterns: ['**/*.{js,css,html,ico,png,svg}'],
+        navigateFallback: 'chat.html',
+        navigateFallbackAllowlist: [
+          new RegExp(`^${(process.env.VITE_BASE_PATH || '/').replace(/[.*+?^${}()|[\]\\]/g, '\\$&')}`),
+        ],
+      },
+      includeAssets: [
+        'favicon.ico',
+        'apple-touch-icon.png',
+        'mask-icon.svg',
+        'icon-192.png',
+        'icon-512.png',
+        'icon-maskable-192.png',
+        'icon-maskable-512.png',
+      ],
+      manifest: {
+        name: 'Chat — Encrypted',
+        short_name: 'Chat',
+        description: 'End-to-end encrypted Nostr chat',
+        theme_color: '#16a34a',
+        background_color: '#ffffff',
+        display: 'standalone',
+        orientation: 'portrait-primary',
+        start_url: process.env.VITE_BASE_PATH || '/',
+        scope: process.env.VITE_BASE_PATH || '/',
+        id: 'chat-app',
+        categories: ['social', 'communication'],
+        lang: 'en',
+        icons: [
+          { src: 'icon-192.png', sizes: '192x192', type: 'image/png', purpose: 'any' },
+          { src: 'icon-512.png', sizes: '512x512', type: 'image/png', purpose: 'any' },
+          { src: 'icon-maskable-192.png', sizes: '192x192', type: 'image/png', purpose: 'maskable' },
+          { src: 'icon-maskable-512.png', sizes: '512x512', type: 'image/png', purpose: 'maskable' },
+        ],
+      },
+    }),
+    ViteImageOptimizer({
+      jpg: { quality: 80 },
+      png: { quality: 80 },
+      webp: { lossless: true },
+    }),
+    mode === 'analyze' &&
+      visualizer({
+        open: true,
+        filename: 'dist-chat/stats.html',
+        gzipSize: true,
+        brotliSize: true,
+      }),
+  ],
+  resolve: {
+    alias: {
+      '@': fileURLToPath(new URL('./src', import.meta.url)),
+      '@/app.config': fileURLToPath(new URL('./src/chat-app/app.config.ts', import.meta.url)),
+    },
+  },
+  build: {
+    outDir: 'dist-chat',
+    rollupOptions: {
+      input: 'chat.html',
+      output: {
+        manualChunks: {
+          'vue-vendor': ['vue', 'vue-router', 'pinia'],
+          'ui-vendor': ['radix-vue', '@vueuse/core'],
+          'shadcn': ['class-variance-authority', 'clsx', 'tailwind-merge'],
+        },
+      },
+    },
+    chunkSizeWarningLimit: 1000,
+  },
+}))