feat(blog): add blog section and rss feed

- Add blog content collection schema and welcome post
- Create blog index, post layout components, and dynamic routing
- Add `@astrojs/rss` dependency and implement RSS feed generation
- Add blog links to header and footer navigation
- Update changelog with Gemini 3.1 Pro enhancement notes

src/pages/rss.xml.ts

@@ -0,0 +1,22 @@
+import type { APIContext } from 'astro';
+import rss from '@astrojs/rss';
+import { getCollection } from 'astro:content';
+
+export async function GET(context: APIContext) {
+  const posts = await getCollection('blog', ({ data }) => {
+    return import.meta.env.PROD ? data.draft !== true : true;
+  });
+
+  return rss({
+    title: 'Zaguán Blade Blog',
+    description: 'Latest news, tutorials, and insights about AI-powered development with Zaguán Blade.',
+    site: context.site ?? 'https://zblade.dev',
+    items: posts.map((post) => ({
+      title: post.data.title,
+      pubDate: post.data.pubDate,
+      description: post.data.description,
+      link: `/blog/${post.slug}/`,
+    })),
+    customData: `<language>en-us</language>`,
+  });
+}