[apps/code] Check that app can be exited before switching to DFU

This fixes the following crash: create a script which contains only
"input()". Execute it, then while in the input, plug in the calculator.
When un-plugging it, the device crashes.

apps/code/app.h

@@ -37,6 +37,13 @@ public:
     ScriptStore m_scriptStore;
   };
   ~App();
+  bool prepareForExit() override {
+    if (m_consoleController.inputRunLoopActive()) {
+      m_consoleController.terminateInputLoop();
+      return false;
+    }
+    return true;
+  }
   StackViewController * stackViewController() { return &m_codeStackViewController; }
   ConsoleController * consoleController() { return &m_consoleController; }