chore: add .gitattributes to normalize bun.lock and text line endings

.gitattributes

@@ -0,0 +1,11 @@
+# Handle line endings automatically for files detected as text
+* text=auto
+
+# Lockfile must use LF across all platforms for Bun consistency
+bun.lock text eol=lf
+
+# Shell scripts must use LF
+*.sh text eol=lf
+
+# Windows batch scripts must use CRLF
+*.bat text eol=crlf