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/tests/account.spec.ts

@@ -6,6 +6,7 @@ import { updateUser } from '../services/database'
 
 test.describe('Account page', () => {
   test('should edit user info properly', async ({ page }) => {
+    await updateUser({ name: 'Default Name' })
     await page.goto('/account')
     const saveButton = page.locator('button:has-text("Save")')
     await expect(saveButton).toBeHidden()