daemon version check, idle mining control, bootstrap mirror, import key paste, and cleanup

- Add startup binary version checking for dragonxd/xmrig
- Display daemon version in UI
- Add idle mining thread count adjustment
- Add bootstrap mirror option (bootstrap2.dragonx.is) in setup wizard
- Add paste button to import private key dialog with address validation
- Add z-address generation UI feedback (loading indicator)
- Add option to delete blockchain data while preserving wallet.dat
- Add font scale slider hotkey tooltip (Ctrl+Plus/Ctrl+Minus)
- Fix Windows RPC auth: trim \r from config values, add .cookie fallback
- Fix connection status message during block index loading
- Improve application shutdown to prevent lingering background process

src/main.cpp

@@ -1800,6 +1800,17 @@ int main(int argc, char* argv[])
     // while background cleanup (thread joins, RPC disconnect) continues.
     SDL_HideWindow(window);
 
+    // Watchdog: if cleanup takes too long the process lingers without a
+    // window, showing up as a "Background Service" in Task Manager.
+    // Force-exit after 3 seconds — all critical state (settings, daemon
+    // stop) was handled in beginShutdown().
+    std::thread([]() {
+        std::this_thread::sleep_for(std::chrono::seconds(3));
+        fflush(stdout);
+        fflush(stderr);
+        _Exit(0);
+    }).detach();
+
     // Final cleanup (daemon already stopped by beginShutdown)
     app.shutdown();
 #ifdef DRAGONX_USE_DX11