Add .gitattributes for consistent line endings

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.gitattributes

@@ -0,0 +1,26 @@
+# Normalize line endings automatically
+* text=auto
+
+# Explicitly declare text files
+*.cs      text
+*.csproj  text
+*.slnx    text
+*.json    text
+*.md      text
+*.txt     text
+*.html    text
+*.css     text
+*.js      text
+*.ps1     text
+*.targets text
+*.config  text
+
+# Designer/resource files stay as-is
+*.resx    text
+
+# Binary files
+*.ico     binary
+*.png     binary
+*.jpg     binary
+*.zip     binary
+*.dll     binary