Add reusable layout partials for easier page creation

- Create content-card-section.html partial for card-based content
- Create step-by-step-section.html partial for process steps
- Create contact-section.html partial for contact information
- Create main-content-section.html general purpose partial that combines all elements
- Add simplified examples using the new partials (acheter-credit-simple and commande-sim-simple)
- These partials follow the existing site theme and make creating new pages much faster

layouts/partials/step-by-step-section.html

@@ -0,0 +1,23 @@
+{{ $title := .title }}
+{{ $steps := .steps }}
+
+<div class="container">
+  <div class="row">
+    <div class="col-12">
+      <div class="card mb-4">
+        <div class="card-body">
+          <h2 class="card-title">{{ $title }}</h2>
+          <div class="row">
+            {{ range $index, $step := $steps }}
+            <div class="col-md-{{ div 12 (len $steps) }} text-center mb-3">
+              <div class="step-number">{{ add $index 1 }}</div>
+              <h5>{{ $step.title }}</h5>
+              <p>{{ $step.description }}</p>
+            </div>
+            {{ end }}
+          </div>
+        </div>
+      </div>
+    </div>
+  </div>
+</div>