fix: extract footnote and reference-style URLs in seeAlsoLinks

Bare URLs in footnote definitions ([^1]: https://...) and reference-style
link definitions ([label]: https://...) were not captured by the existing
inline-link regex. Added a second pass with a multiline regex.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

eleventy.config.js

@@ -1400,6 +1400,10 @@ export default function (eleventyConfig) {
       const re = new RegExp(`(?<!!)\\]\\((${escaped}/[^)\\s]+)\\)`, "g");
       let m;
       while ((m = re.exec(content)) !== null) add(m[1]);
+      // Also extract reference-style link definitions and bare footnote URLs:
+      // [^1]: https://blog.giersig.eu/...  or  [label]: https://blog.giersig.eu/...
+      const reRef = new RegExp(`^\\[[^\\]]+\\]:\\s+(${escaped}/[^\\s]+)`, "gm");
+      while ((m = reRef.exec(content)) !== null) add(m[1]);
     } catch { /* ignore */ }
     return result;
   });