chore: add .gitattributes to normalize line endings

Default to LF, force CRLF for Windows script/solution files, and mark
common binary types — silences the CRLF-on-commit warnings.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

.gitattributes

@@ -0,0 +1,16 @@
+* text=auto eol=lf
+
+*.sln  text eol=crlf
+*.slnx text eol=crlf
+*.cmd  text eol=crlf
+*.bat  text eol=crlf
+*.ps1  text eol=crlf
+
+*.png  binary
+*.jpg  binary
+*.jpeg binary
+*.gif  binary
+*.ico  binary
+*.zip  binary
+*.exe  binary
+*.dll  binary