Add .gitattributes: force LF for shell + Dockerfile

防 Windows 本地 CRLF 检出 → 直接 docker build 时 init.sh shebang 报
`/bin/bash^M: No such file`。当前 deploy/sandbox/ 文件在 repo 已是 LF
(git show 验过),本文件锁住未来贡献者环境。

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.gitattributes

@@ -0,0 +1,6 @@
+# Force LF for files consumed by Linux toolchains (docker build / bash).
+# Windows dev checkouts otherwise get CRLF via core.autocrlf, breaking
+# `#!/bin/bash` and Dockerfile heredocs in container.
+*.sh         text eol=lf
+Dockerfile   text eol=lf
+*.Dockerfile text eol=lf