fix: complete help guide i18n — all body text translated

- Help badges, stat labels, headings tagged
- All <li> descriptions after <strong> wrapped in data-i18n
- 30 text fragments in help body tagged + EN translations
- 791 locale keys total, 0 untranslated help keys
- Emojis preserved in nav items

frontend/index.html

@@ -2729,7 +2729,7 @@
                         </section>
 
                         <section class="help-section" id="help-interface">
-                            <h2>🧭 Interface utilisateur</h2>
+                            <h2 data-i18n="help.nav_interface">🧭 Interface utilisateur</h2>
 
                             <h3 data-i18n="help.header_section">En-tête</h3>
                             <pdata-i18n="auto.209c5490">
@@ -2739,7 +2739,7 @@
                             <ul>
                                 <li>
                                     <strong data-i18n="help.hamburger_btn">Bouton menu hamburger</strong>
-                                    (mobile) : Affiche/masque la sidebar
+                                    : <span data-i18n="help.desc_hamburger">obile) : Affiche/masque la sidebar</span>
                                 </li>
                                 <li>
                                     <strong data-i18n="help.sidebar_toggle_btn">Bouton toggle sidebar</strong>