Fix start.sh execution issues

- Add .gitattributes to force LF line endings for shell scripts
- Ensure start.sh is executable

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.gitattributes

@@ -0,0 +1,6 @@
+# Ensure shell scripts always have LF line endings
+*.sh text eol=lf
+
+# Keep these as LF regardless of platform
+Dockerfile text eol=lf
+nginx.conf text eol=lf