Add Insights blog section with two founding articles

- Create articles/ directory with hub index page (newest-first card grid)
- Add Article 1: "Why We Built HOA LedgerIQ" (March 16, 2026, founder story)
- Add Article 2: "5 Financial Blind Spots Putting Your HOA at Risk" (April 1, 2026, use case)
- Both articles include screenshot carousel, article CTA, prev/next nav, and full SEO meta
- Add blog/article CSS to styles.css (hub hero, card grid, article prose, showcase, CTA)
- Add "Insights" nav link to index.html, reserve-study-software.html, investment-management.html
- Add "Insights" to footer Pages column on all pages (index.html gets a Pages column added)
- Add articles/ pages to sitemap.xml with appropriate priorities and lastmod dates

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

reserve-study-software.html

@@ -40,6 +40,7 @@
         <li><a href="#features">Features</a></li>
         <li><a href="#comparison">Comparison</a></li>
         <li><a href="index.html#pricing">Pricing</a></li>
+        <li><a href="articles/">Insights</a></li>
       </ul>
       <a href="index.html#preview-signup" class="btn btn-primary nav-btn">Get Early Access</a>
       <a href="https://app.hoaledgeriq.com" class="btn btn-outline nav-btn nav-login" target="_blank" rel="noopener">Login</a>
@@ -247,6 +248,7 @@
           <div class="footer-col-title">Pages</div>
           <a href="investment-management.html">Investment Management</a>
           <a href="reserve-study-software.html">Reserve Studies</a>
+          <a href="articles/">Insights</a>
         </div>
         <div class="footer-col">
           <div class="footer-col-title">Legal</div>