docs(changelog): update version labels and dates for v0.4.0 and v0.3.4

- Change v0.4.0 card to “latest” and set proper release date.
- Convert v0.3.4 card to “previous” and adjust badge class.

src/pages/changelog.astro

@@ -24,13 +24,13 @@ import BaseLayout from '../layouts/BaseLayout.astro';
     <!-- v0.4.0 Section -->
     <section class="changelog-section">
       <div class="container">
-        <div class="version-card version-development">
+        <div class="version-card version-latest">
           <div class="version-header">
             <div class="version-info">
                <h2 class="version-number">v0.4.0</h2>
-              <span class="version-date">TBD</span>
+              <span class="version-date">March 11, 2026</span>
             </div>
-            <span class="version-badge badge-development">Development</span>
+            <span class="version-badge badge-latest">Latest</span>
           </div>
           
            <div class="version-content">
@@ -109,13 +109,13 @@ import BaseLayout from '../layouts/BaseLayout.astro';
     <!-- v0.3.4 Section -->
     <section class="changelog-section">
       <div class="container">
-        <div class="version-card version-latest">
+        <div class="version-card version-previous">
                     <div class="version-header">
                       <div class="version-info">
                         <h2 class="version-number">v0.3.4</h2>
                         <span class="version-date">2026-03-05</span>
                       </div>
-            <span class="version-badge badge-latest">Latest</span>
+                      <span class="version-badge badge-previous">Previous</span>
                     </div>
           
           <div class="version-content">