feat: add notifications and project shares features

- Backend: notifications + shares routes, DB tables, SqliteAdapter methods
- Frontend: NotificationPanel (bell icon + dropdown), ShareDialog, Dashboard integration
- Styles: notification + share dialog CSS

frontend/src/pages/Dashboard.tsx

@@ -3,6 +3,8 @@
  */
 import { useState, useEffect, useCallback } from 'react';
 import { useAuth } from '../contexts/AuthContext';
+import { NotificationPanel } from '../components/NotificationPanel';
+import { ShareDialog } from '../components/ShareDialog';
 
 const API_BASE = import.meta.env.VITE_API_BASE || '';
 
@@ -25,6 +27,7 @@ export function Dashboard({ onOpenProject }: DashboardProps) {
   const [showCreate, setShowCreate] = useState(false);
   const [newName, setNewName] = useState('');
   const [newDesc, setNewDesc] = useState('');
+  const [shareProjectId, setShareProjectId] = useState<string | null>(null);
 
   const fetchProjects = useCallback(async () => {
     setLoading(true);
@@ -86,7 +89,10 @@ export function Dashboard({ onOpenProject }: DashboardProps) {
           <h1>Web CAD</h1>
           <span className="dashboard-user">{user?.name} ({user?.role})</span>
         </div>
-        <button className="dashboard-logout" onClick={logout}>Abmelden</button>
+        <div className="dashboard-header-actions">
+          <NotificationPanel token={token!} />
+          <button className="dashboard-logout" onClick={logout}>Abmelden</button>
+        </div>
       </header>
 
       <div className="dashboard-content">
@@ -133,18 +139,33 @@ export function Dashboard({ onOpenProject }: DashboardProps) {
                 {project.description && <p>{project.description}</p>}
                 <div className="dashboard-project-meta">
                   <span>Erstellt: {new Date(project.created_at).toLocaleDateString('de-DE')}</span>
-                  <button
-                    className="dashboard-delete-btn"
-                    onClick={(e) => handleDelete(project.id, e)}
-                  >
-                    Löschen
-                  </button>
+                  <div className="dashboard-project-actions">
+                    <button
+                      className="dashboard-share-btn"
+                      onClick={(e) => { e.stopPropagation(); setShareProjectId(project.id); }}
+                    >
+                      Teilen
+                    </button>
+                    <button
+                      className="dashboard-delete-btn"
+                      onClick={(e) => handleDelete(project.id, e)}
+                    >
+                      Löschen
+                    </button>
+                  </div>
                 </div>
               </div>
             ))}
           </div>
         )}
       </div>
+
+      <ShareDialog
+        token={token!}
+        projectId={shareProjectId ?? ''}
+        open={!!shareProjectId}
+        onClose={() => setShareProjectId(null)}
+      />
     </div>
   );
 }