fix: i18n help introduction hero — badges + stat labels

- 5 feature tag badges: data-i18n on span.help-badge
- 3 stat labels: Experience, Search → English
- Access label fixed with dedicated key
- All EN translations provided

frontend/index.html

@@ -2691,38 +2691,40 @@
                                     moderne et responsive.
                                 </p>
                                 <div class="help-badges">
-                                    <span class="help-badge"
+                                    <span class="help-badge" data-i18n="help.welcome_tag1"
                                         >⚡ Navigation rapide</span
                                     >
-                                    <span class="help-badge"
+                                    <span class="help-badge" data-i18n="help.welcome_tag2"
                                         >🗂️ Multi-vault</span
                                     >
-                                    <span class="help-badge"
+                                    <span class="help-badge" data-i18n="help.welcome_tag3"
                                         >🏷️ Tags intelligents</span
                                     >
-                                    <span class="help-badge"
+                                    <span class="help-badge" data-i18n="help.welcome_tag4"
                                         >📝 Lecture et édition</span
                                     >
-                                    <span class="help-badge"
+                                    <span class="help-badge" data-i18n="help.welcome_tag5"
                                         >🔍 Recherche TF-IDF</span
                                     >
                                 </div>
                             </div>
                             <div class="help-hero-visual" aria-hidden="true">
                                 <div class="help-stat-card">
-                                    <span class="help-stat-label"
+                                    <span class="help-stat-label" data-i18n="help.experience"
                                         >Expérience</span
                                     >
                                     <strong data-i18n="help.simple">Simple</strong>
                                 </div>
                                 <div class="help-stat-card">
-                                    <span class="help-stat-label"
+                                    <span class="help-stat-label" data-i18n="help.search_bar"
                                         >Recherche</span
                                     >
                                     <strong data-i18n="help.instant">Instantanée</strong>
                                 </div>
                                 <div class="help-stat-card">
-                                    <span class="help-stat-label" data-i18n="auto.ca0aceee">Accès</span>
+                                    <span class="help-stat-label" data-i18n="help.access"
+                                        >Accès</span
+                                    >
                                     <strong data-i18n="help.multi_vault">Multi-vault</strong>
                                 </div>
                             </div>