Extend .gitignore and add .gitattributes for line endings

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.gitattributes

@@ -0,0 +1,6 @@
+# Normalize line endings in the repo; checkout uses the platform default
+* text=auto
+
+*.png binary
+*.jpg binary
+*.bin binary

.gitignore

@@ -10,3 +10,13 @@ src/esp32/secrets.h
 
 # Claude Code local settings
 .claude/settings.local.json
+
+# OS files
+Thumbs.db
+desktop.ini
+.DS_Store
+
+# Editor temp / backup files
+*.swp
+*~
+*.bak