chore: add .gitignore to protect config files

.gitignore

@@ -0,0 +1,18 @@
+# Ignore all files under configs/ except files ending with .sample
+/configs/*
+!/configs/*.sample
+
+# Local env files and common secrets
+.env
+.env.local
+*.key
+*.pem
+
+# Build outputs
+/bin/
+/*.exe
+/*.exe~
+
+# Editor temp files
+*~
+.DS_Store