refactor(editor): ♻️ Undo / Redo buttons + structure refacto

Yet another huge refacto... While implementing undo and redo features I understood that I updated the stored typebot too many times (i.e. on each key input) so I had to rethink it entirely. I also moved around some files.

apps/builder/playwright.config.ts

@@ -26,6 +26,7 @@ const config: PlaywrightTestConfig = {
       name: 'Chrome',
       use: {
         ...devices['Desktop Chrome'],
+        viewport: { width: 1400, height: 1000 },
       },
     },
   ],