Simplify fix: only add isInt() check in refresh methods

Changed approach per maintainer feedback - instead of caching signal values,
just add isInt() check before accessing config_["signal"].asInt() in refresh()
methods. This is simpler and more minimal.

Co-authored-by: Alexays <13947260+Alexays@users.noreply.github.com>

include/modules/custom.hpp

@@ -42,7 +42,6 @@ class Custom : public ALabel {
   int pid_;
   util::command::res output_;
   util::JsonParser parser_;
-  int signal_;  // Cached signal value (-1 = disabled) to avoid JSON access in signal handler
 
   util::SleeperThread thread_;
 };

include/modules/image.hpp

@@ -33,7 +33,6 @@ class Image : public AModule {
   int size_;
   std::chrono::milliseconds interval_;
   util::command::res output_;
-  int signal_;  // Cached signal value (-1 = disabled) to avoid JSON access in signal handler
 
   util::SleeperThread thread_;
 };