Compute the footer copyright range from the earliest post's year

"© 2021-2026 andwati" — start year is the minimum date across all
published writings (src/lib/copyright-year.ts), not a hand-maintained
config value like the old zola.toml's copyright_start_year. Updates
itself automatically both as the year changes and if an older post is
ever added.

apps/site/src/layouts/Base.astro

@@ -3,6 +3,7 @@ import "@fontsource-variable/fraunces";
 import "@fontsource-variable/newsreader";
 import "@fontsource/jetbrains-mono";
 import "../styles/global.css";
+import { copyrightYearRange } from "../lib/copyright-year";
 import { siteConfig } from "../site.config";
 
 interface Props {
@@ -14,6 +15,7 @@ interface Props {
 const { title, description, wide = false } = Astro.props;
 const metaDescription = description ?? siteConfig.description;
 const currentPath = Astro.url.pathname;
+const copyrightRange = await copyrightYearRange();
 ---
 
 <html lang="en">
@@ -131,7 +133,7 @@ const currentPath = Astro.url.pathname;
         <slot />
       </main>
       <footer>
-        <p class="meta">© {new Date().getFullYear()} {siteConfig.author}</p>
+        <p class="meta">© {copyrightRange} {siteConfig.author}</p>
         <nav aria-label="Social">
           <a href={siteConfig.social.github} class="meta" rel="me noopener" target="_blank">GitHub</a>
           <a href={siteConfig.social.twitter} class="meta" rel="me noopener" target="_blank">Twitter</a>

apps/site/src/lib/copyright-year.ts

@@ -0,0 +1,17 @@
+import { getCollection } from "astro:content";
+
+/** "2021–2026" (earliest published writing's year through now), or just
+ * "2026" if that's the same year — computed from real content, not a
+ * hand-maintained start-year config value. */
+export async function copyrightYearRange(): Promise<string> {
+  const writings = await getCollection("writings", ({ data }) => !data.draft);
+  const currentYear = new Date().getFullYear();
+  if (writings.length === 0) return String(currentYear);
+
+  const startYear = Math.min(
+    ...writings.map((entry) => entry.data.date.getFullYear()),
+  );
+  return startYear === currentYear
+    ? String(currentYear)
+    : `${startYear}–${currentYear}`;
+}