Keep ci-release.sh at LF so it runs on the Gitea runner

Git was set to normalize to CRLF on checkout, which puts a carriage return in the
shebang and breaks the script on Linux. Also documents what User/ holds.

.gitattributes

@@ -0,0 +1,6 @@
+# Shell scripts must keep LF: a CR in the shebang or in a command breaks bash on Linux.
+*.sh text eol=lf
+
+# PowerShell is happy either way, but keep the working tree native on Windows.
+*.ps1 text eol=crlf
+*.cmd text eol=crlf