feat: add custom branding, air-gapped deployment script, and updated self-hosting docs

vite.config.ts

@@ -293,6 +293,9 @@ export default defineConfig(() => {
         context: {
           baseUrl: (process.env.BASE_URL || '/').replace(/\/?$/, '/'),
           simpleMode: process.env.SIMPLE_MODE === 'true',
+          brandName: process.env.VITE_BRAND_NAME || '',
+          brandLogo: process.env.VITE_BRAND_LOGO || '',
+          footerText: process.env.VITE_FOOTER_TEXT || '',
         },
       }),
       languageRouterPlugin(),
@@ -334,6 +337,7 @@ export default defineConfig(() => {
     ],
     define: {
       __SIMPLE_MODE__: JSON.stringify(process.env.SIMPLE_MODE === 'true'),
+      __BRAND_NAME__: JSON.stringify(process.env.VITE_BRAND_NAME || ''),
     },
     resolve: {
       alias: {