chore: gitignore the staged vulkan-1.dll loader

.gitignore

@@ -41,3 +41,8 @@ Thumbs.db
 # NPU runtime bundle: a large binary artifact hosted as a Gitea package, not
 # committed. The folder's README is tracked; the zip is produced locally.
 packaging/npu-runtime/*.zip
+
+# Vulkan loader staged next to the exe / into src-tauri by build.rs for the
+# --features vulkan build (bundled into the installer); a redistributable blob,
+# not committed.
+src-tauri/vulkan-1.dll