feat(05-02): add test articles FR/EN and temporary test page

- content/fr/blog/test-kotlin-syntax.md: FR test article covering all 4 validation criteria
- content/en/blog/test-kotlin-syntax.md: EN version with same slug
- app/pages/test.vue: temporary page at /test for visual checkpoint verification
- Both articles contain: kotlin code block, NuxtImg image, markdown table, 4 callout types

app/pages/test.vue

@@ -0,0 +1,11 @@
+<script setup lang="ts">
+const { data: page } = await useAsyncData('test', () =>
+  queryCollection('blog_fr').path('/blog/test-kotlin-syntax').first()
+)
+</script>
+
+<template>
+  <article class="prose dark:prose-invert max-w-none p-8">
+    <ContentRenderer v-if="page" :value="page" />
+  </article>
+</template>