feat: Rebranding von LeadFlow zu OnyvaLeads

Alle UI-Labels, Dateinamen, API-Bezeichner und package.json auf OnyvaLeads umgestellt.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

components/layout/Sidebar.tsx

@@ -62,7 +62,7 @@ export function Sidebar() {
           <Zap className="w-4 h-4 text-white" />
         </div>
         {!sidebarCollapsed && (
-          <span className="font-bold text-lg tracking-tight text-white">LeadFlow</span>
+          <span className="font-bold text-lg tracking-tight text-white">OnyvaLeads</span>
         )}
       </div>