Add .gitattributes to enforce LF line endings

.gitattributes

@@ -0,0 +1,9 @@
+# Default: normalize all text files to LF in the repo
+* text=auto eol=lf
+
+# Explicitly handle common file types
+*.js    text eol=lf
+*.json  text eol=lf
+*.md    text eol=lf
+*.yml   text eol=lf
+*.env   text eol=lf