♻️(backend) simplify the template

For the first version, we will use a simple template.
Only the gouv logo will be displayed.

src/backend/demo/data/template/code.txt

@@ -1,21 +1,10 @@
 <page size="A4">
   <div class="header">
-    <image src="https://upload.wikimedia.org/wikipedia/fr/7/72/Logo_du_Gouvernement_de_la_R%C3%A9publique_fran%C3%A7aise_%282020%29.svg"/>
-    <h2 class="header-title">Direction<br/>Interministérielle<br/>du numérique</h2>
-  </div>
-  <div class="second-row">
-    <div class="who-ref">
-      <div class="who">La directrice</div>
-      <p class="ref">Réf: 1200001</p>
-    </div>
-    <div class="date">Paris, le 28/09/2023</div>
-  </div>
-  <div class="third-row">
-    <h4 class="title">Note</h4>
-    <h5 class="subtitle">à Monsieur le Premier Ministre</h5>
+    <img
+      src="https://upload.wikimedia.org/wikipedia/fr/7/72/Logo_du_Gouvernement_de_la_R%C3%A9publique_fran%C3%A7aise_%282020%29.svg"
+    />
   </div>
   <div class="content">
-    <div class="object">Objet: Generated PDF</div>
     <div class="body">{{ body }}</div>
   </div>
-</page>
+</page>

src/backend/demo/data/template/css.txt

@@ -2,54 +2,14 @@ body {
   background: white; 
   font-family: arial
 }
-img {
-  width: 5cm;
-  margin-left: -0.4cm;
-}
 .header {
   display: flex;
   justify-content: space-between;
 }
-.header-title {
-  text-align: right;
-  margin-top: 3rem;
-  font-size: 1.2rem;
-}
-.second-row {
-  display: flex;
-  justify-content: space-between;
-  margin-top: 1.2cm;
-}
-.ref {
-  margin-top: 0;
-}
-.who {
-  font-weight: medium;
-}
-.date, .ref {
-  font-size: 12px;
-}
-.title, .subtitle {
-  margin: 0;
-}
-.subtitle {
-  font-weight: normal;
-}
-.object {
-  font-weight: bold;
-  margin-bottom: 1.2cm;
-  margin-top: 3rem
+.header img {
+  width: 5cm;
+  margin-left: -0.4cm;
 }
 .body{
   margin-top: 1.5rem
 }
-h1 {
-  font-size: 18px;
-}
-h2 {
-  font-size: 14px;
-}
-p {
-  text-align: justify;
-  ligne-height: 0.8;
-}