feat: add configurable host binding for server and Vite dev server

- Add HOST environment variable (default: 0.0.0.0) to allow binding to specific network interfaces
- Update server to listen on configurable host instead of hardcoded localhost
- Update Vite dev server to respect HOST environment variable
- Enhanced server startup banner to display listening address
- Updated .env.example and CLAUDE.md documentation

Fixes #536

Co-authored-by: Web Dev Cody <webdevcody@users.noreply.github.com>

apps/ui/vite.config.mts

@@ -65,6 +65,7 @@ export default defineConfig(({ command }) => {
       },
     },
     server: {
+      host: process.env.HOST || '0.0.0.0',
       port: parseInt(process.env.TEST_PORT || '3007', 10),
     },
     build: {