chore(git): pin *.sh to LF via .gitattributes

Shell scripts are run by bash (WSL/Linux/CI). With core.autocrlf=true the
working tree gets CRLF, and bash then fails on the stray CR: the packing step
of build.bat died with

    pack_system_image.sh: line 13: $'\r': command not found
    pack_system_image.sh: line 14: set: pipefail\r: invalid option name

core.autocrlf is a per-clone setting and is not shared, so the only reliable
fix is a repository-level attribute. Pin *.sh to LF for every checkout.

.gitattributes

@@ -1 +1,8 @@
 *.mp4 filter=lfs diff=lfs merge=lfs -text
+
+# Shell scripts are executed by bash (WSL / Linux / CI). CRLF line endings
+# break them outright ("$'\r': command not found", and a stray CR in a shebang
+# or in `set -euo pipefail` makes the whole script unrunnable) - the packing
+# step of this project's build died on exactly that. Pin LF for every checkout
+# regardless of the developer's core.autocrlf setting.
+*.sh text eol=lf