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>

sitemap.xml

@@ -34,6 +34,28 @@
         <priority>0.95</priority>
     </url>
     
+    <!-- Insights / Blog -->
+    <url>
+        <loc>https://www.hoaledgeriq.com/articles/</loc>
+        <lastmod>2026-04-01</lastmod>
+        <changefreq>weekly</changefreq>
+        <priority>0.85</priority>
+    </url>
+
+    <url>
+        <loc>https://www.hoaledgeriq.com/articles/hoa-financial-blind-spots</loc>
+        <lastmod>2026-04-01</lastmod>
+        <changefreq>monthly</changefreq>
+        <priority>0.80</priority>
+    </url>
+
+    <url>
+        <loc>https://www.hoaledgeriq.com/articles/why-we-built-hoa-ledgeriq</loc>
+        <lastmod>2026-03-16</lastmod>
+        <changefreq>monthly</changefreq>
+        <priority>0.75</priority>
+    </url>
+
     <!-- Legal Pages -->
     <url>
         <loc>https://www.hoaledgeriq.com/privacy.html</loc>