feat(FN-2044): propagate model favorites through QuickChatFAB

- Extend QuickChatFAB props with favorite providers/models and favorite toggle callbacks
- Forward favorite state and handlers to the model override CustomModelDropdown
- Wire App.tsx favorite provider/model state and toggle handlers into QuickChatFAB
- Add QuickChatFAB tests for pinned favorite models, provider favorites, and toggle callback behavior

packages/dashboard/app/components/ChatView.tsx

@@ -794,15 +794,6 @@ export function ChatView({ projectId, addToast }: ChatViewProps) {
 
   // Render empty state (no active session)
   const renderEmptyState = () => {
-    if (showNewDialog) {
-      return (
-        <NewChatDialog
-          onClose={() => setShowNewDialog(false)}
-          onCreate={handleCreateSession}
-        />
-      );
-    }
-
     return (
       <div className="chat-empty-state">
         <MessageSquare size={48} strokeWidth={1.5} />