Copy uninstall.sh to /data/truecloud-patch/ on install

Users who delete the cloned repo after install had no way to uninstall
without re-cloning. Now install.sh copies uninstall.sh to PATCH_DIR
alongside recover.sh, so the uninstall path is always the stable
/data/truecloud-patch/uninstall.sh. README updated to match.

README.md

@@ -147,7 +147,7 @@ Get an API key from **System → API Keys → Add**.
 ## Uninstall
 
 ```bash
-bash /path/to/truenas-truecloud-patch/uninstall.sh
+bash /data/truecloud-patch/uninstall.sh
 ```
 
 Removes the PREINIT hook, `sitecustomize.py`, and restores the original UI