refactor: rename astro.config.mjs to astro.config.ts

Astro 5 natively supports TypeScript config files. Using .ts gives us
type-checking and better IDE support without needing jiti.

Addresses review feedback:
https://github.com/Comfy-Org/ComfyUI_frontend/pull/10140#discussion_r2951185092

apps/website/astro.config.mjs

@@ -1,24 +0,0 @@
-import { defineConfig } from 'astro/config'
-import vue from '@astrojs/vue'
-import tailwindcss from '@tailwindcss/vite'
-
-export default defineConfig({
-  site: 'https://comfy.org',
-  output: 'static',
-  integrations: [vue()],
-  vite: {
-    plugins: [tailwindcss()]
-  },
-  build: {
-    assetsPrefix: process.env.VERCEL_URL
-      ? `https://${process.env.VERCEL_URL}`
-      : undefined
-  },
-  i18n: {
-    locales: ['en', 'zh-CN'],
-    defaultLocale: 'en',
-    routing: {
-      prefixDefaultLocale: false
-    }
-  }
-})