fix: restore strings import in caveman_safety

The import was incorrectly removed — strings.ToLower,
strings.Contains, strings.TrimSpace, and strings.Builder
are all used in this file.

Author: Patel230

internal/compress/caveman_safety.go

@@ -1,6 +1,7 @@
 package compress
 
 import (
+	"strings"
 	"unicode"
 )