fix: use rollupConfig.external to prevent Nitro from bundling better-sqlite3

nitro.externals.external doesn't prevent Rollup from inlining the
require. rollupConfig.external tells Rollup directly to leave the
import as-is, so Node resolves it from node_modules at runtime.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

nuxt.config.ts

@@ -10,7 +10,7 @@ export default defineNuxtConfig({
 
   nitro: {
     experimental: { tasks: true },
-    externals: {
+    rollupConfig: {
       external: ['better-sqlite3'],
     },
   },