feat: badge emoji partagé (noir & blanc) dans l'arborescence + sidebar «Par moi» inclut is_shared

- board/dashboard: helper _load_shared_sidebar_pages intégrant les pages marquées is_shared directement
- _workspace_tree_macro: badge 👥 N&B sur les fichiers partagés du tree du sidebar
- local_workspace: badge 👥 en noir & blanc
- static/css/app.css: style .page-shared-badge

app/templates/_workspace_tree_macro.html

@@ -27,6 +27,7 @@
     <span style="width:12px;flex-shrink:0;"></span>
     {% endif %}
     <span class="page-icon">{% set valid_icons = ["folder","file","star","link","trash","book","home","settings","lock","globe","image","edit","calendar","users","user","search","tag","bar-chart","grid","list","align-left","zap"] %}{% if page.icon in valid_icons %}{{ fd_icon(page.icon,14) }}{% elif page.is_folder %}{{ fd_icon("folder",14) }}{% else %}{{ fd_icon("file",14) }}{% endif %}</span>
+    {% if page.is_shared %}<span class="page-shared-badge" title="Partagé">👥</span>{% endif %}
     {% if page.is_folder %}
     <span class="page-name tree-folder-link" 
           @click.stop="navigateToFolder({{ page.db_id }})"