Fix renamed repository installation path

Update the README clone URL and local directory name to match the current christmas-tree-card repository.

Author: Yangjunjie-Lin

README.md

@@ -29,8 +29,8 @@ A polished desktop Christmas tree rendered from thousands of tiny animated parti
 Clone the repository and install the runtime dependency:
 
 ```bash
-git clone https://github.com/yangjunjie-lin/merry-christmas.git
-cd merry-christmas
+git clone https://github.com/Yangjunjie-Lin/christmas-tree-card.git
+cd christmas-tree-card
 python -m venv .venv
 ```