fix(mango): reconnect IPC event thread on disconnect

The IPC event thread had no reconnect: on POLLHUP/POLLERR/POLLNVAL or
read()==0/error it broke out of the loop and the thread exited
permanently, freezing every mango module with stale content until
Waybar was restarted. Wrap the connect + poll/read loop in a reconnect
loop with a bounded 2s backoff, re-establishing the socket and resuming
on disconnect, modeled on the niri backend.

Add an atomic running_ flag so the worker exits cleanly on teardown;
the destructor now sets it false before closing the socket so the
worker breaks out and joins, and leaves the final close to the
destructor to avoid a double close.

include/modules/mango/backend.hpp

@@ -1,6 +1,7 @@
 // include/modules/mango/backend.hpp
 #pragma once
 
+#include <atomic>
 #include <list>
 #include <mutex>
 #include <string>
@@ -52,6 +53,7 @@ class IPC {
 
   static Json::Value sendCommand(const std::string& cmd);
 
+  std::atomic<bool> running_ = true;
   int sockfd_ = -1;
   std::thread ipc_thread_;
   mutable std::mutex data_mutex_;