feat: implement blog section with first article

Add blog functionality to the Hugo site:
- Create blog content structure (content/blog/)
- Add blog list and single templates (layouts/blog/)
- Add blog navigation to menu
- Publish first article: "KI Generierte Website - ein Praxisbeispiel"
- Support multilingual structure (German/English)
- Add code block styling for blog posts

The blog section is now accessible at /de/blog/ and /en/blog/
with proper navigation, responsive design, and semantic HTML.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

layouts/blog/list.html

@@ -0,0 +1,45 @@
+{{ define "main" }}
+<div class="container py-5">
+  <div class="row">
+    <div class="col-lg-8 mx-auto">
+      <header class="mb-5">
+        <h1>{{ .Title }}</h1>
+        {{ if .Description }}
+          <p class="lead text-muted">{{ .Description }}</p>
+        {{ end }}
+      </header>
+
+      <div class="blog-list">
+        {{ range .Pages }}
+          <article class="mb-5 pb-5 border-bottom">
+            <header class="mb-3">
+              <h2 class="h3">
+                <a href="{{ .RelPermalink }}" class="text-decoration-none">{{ .Title }}</a>
+              </h2>
+              <time datetime="{{ .Date.Format "2006-01-02" }}" class="text-muted">
+                {{ .Date.Format "2. January 2006" }}
+              </time>
+            </header>
+
+            {{ if .Description }}
+              <p class="lead">{{ .Description }}</p>
+            {{ else if .Summary }}
+              <div class="summary">
+                {{ .Summary }}
+              </div>
+            {{ end }}
+
+            <a href="{{ .RelPermalink }}" class="btn btn-outline-primary">
+              {{ if eq $.Language.Lang "de" }}
+                Weiterlesen
+              {{ else }}
+                Read more
+              {{ end }}
+            </a>
+          </article>
+        {{ end }}
+      </div>
+    </div>
+  </div>
+</div>
+{{ end }}