fix(og-image): bump 6.3.5 + skip OG prerender

nuxt-og-image 6.3.5 fixes signed URL generation when strict+secret are
set. But CI has no secret, so URLs stay in hash mode and orphaned hashes
fail. Adding nitro.prerender.ignore for /_og/ ensures OG images are
never prerendered regardless of environment — they're runtime-only (ISR).

Author: harlan-zw

nuxt.config.ts

@@ -257,6 +257,12 @@ export default defineNuxtConfig({
     replace: {
       'import.meta.test': isTest,
     },
+    prerender: {
+      // OG images are runtime-only (ISR). Without a signing secret (CI),
+      // URLs use hash mode which requires the source page to be prerendered
+      // first — skip to avoid orphaned hash 404s.
+      ignore: ['/_og/'],
+    },
   },
 
   fonts: {