Fix CRLF breakage in Linux build scripts

The Linux build host reads these scripts from a shared mount of the
Windows working tree, where autocrlf produces CRLF line endings. bash
then failed on `set -o pipefail` (trailing CR in the option name), and
the version parsed from version.go carried a trailing CR into the Docker
tag ("...:0.6.0\r": invalid reference format).

- Add .gitattributes forcing LF on *.sh so Windows checkouts stay LF.
- Strip CR from the version extraction in all three Linux build scripts.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

scripts/build-release-linux.sh

@@ -9,7 +9,7 @@ script_dir="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
 repo_root="$(cd "${script_dir}/.." && pwd)"
 cd "$repo_root"
 
-version="$(sed -n 's/^var Version = "\(.*\)"/\1/p' src/app/version.go)"
+version="$(sed -n 's/^var Version = "\(.*\)"/\1/p' src/app/version.go | tr -d '\r')"
 version="${version:-0.0.0-dev}"
 tag="gitea.mixdep.ru/mix/gosentry-builder:${version}"