Add forward declaration for csv_quote

Introduce a forward declaration for std::string csv_quote(const std::string&) at the top of cmd_sky.cpp so the function can be referenced before its definition, preventing implicit-declaration/compile issues and clarifying intent.

Author: lzray-universe

src/query/cmd_sky.cpp

@@ -1,5 +1,7 @@
 namespace{
 
+std::string csv_quote(const std::string&s);
+
 std::string csv_num_or_empty(double value){
 	return std::isfinite(value)?format_num(value):"";
 }