Add blog post and support pubDate/tags

Add new post "After the Silence". Update content schema to use
pubDate and include tags (default empty). Update blog listing,
post page and start page to use pubDate, render tag lists, and
compute/show up to two related posts by tag overlap. Misc
formatting and small display tweaks.

src/content/config.ts

@@ -1,13 +1,14 @@
-import { z, defineCollection } from 'astro:content';
+import { z, defineCollection } from "astro:content";
 
 const blog = defineCollection({
-  type: 'content',
-  schema: z.object({
-    title: z.string(),
-    date: z.coerce.date(),
-    description: z.string(),
-    draft: z.boolean().optional().default(false),
-  }),
+    type: "content",
+    schema: z.object({
+        title: z.string(),
+        description: z.string(),
+        pubDate: z.coerce.date(),
+        tags: z.array(z.string()).default([]),
+        draft: z.boolean().optional().default(false),
+    }),
 });
 
 export const collections = { blog };