Add .gitignore to prevent sensitive files from being committed

.gitignore

@@ -0,0 +1,43 @@
+# ============================================================================
+# .gitignore - Open4Neptune Configs
+# Prevents sensitive files from being committed
+# ============================================================================
+
+# Backup files
+*.cfg.backup*
+*.backup*
+*.bak
+*.old
+
+# Local user settings (should NOT be committed)
+user_settings.cfg
+hardware.cfg
+
+# IDE / Editor
+.vscode/
+.idea/
+*.swp
+*.swo
+*~
+
+# OS files
+.DS_Store
+Thumbs.db
+
+# Logs
+*.log
+
+# Temporary files
+tmp/
+temp/
+*.tmp
+
+# ============================================================================
+# SECURITY: Never commit these!
+# ============================================================================
+# - Tokens / API Keys
+# - Passwords
+# - Private keys
+# - .git/config (contains remote URLs with credentials)
+# - Any file with "secret", "token", "password" in name
+# ============================================================================