fix: vertically center sections for fixed header/footer and stabilize diagram layout

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: aymuos15

styles/base.css

@@ -32,7 +32,7 @@ main {
     max-width: var(--content-max-width);
     width: 100%;
     margin: 0 auto;
-    padding: 0 2rem;
+    padding: 3.5rem 2rem 3rem;
 }
 
 a {

styles/components/research.css

@@ -90,6 +90,7 @@
     gap: 4px;
     height: 150px;
     padding-bottom: 14px;
+    flex-shrink: 0;
 }
 
 .diagram-bar-col {
@@ -136,6 +137,8 @@
     font-size: 0.45rem;
     color: var(--text-secondary);
     white-space: nowrap;
+    min-width: 3.2em;
+    text-align: center;
     transition: color 0.3s;
 }