Activity as standard object (#6219)

In this PR I layout the first steps to migrate Activity to a traditional
Standard objects

Since this is a big transition, I'd rather split it into several
deployments / PRs

<img width="1512" alt="image"
src="https://github.com/user-attachments/assets/012e2bbf-9d1b-4723-aaf6-269ef588b050">

---------

Co-authored-by: Charles Bochet <charles@twenty.com>
Co-authored-by: bosiraphael <71827178+bosiraphael@users.noreply.github.com>
Co-authored-by: Weiko <corentin@twenty.com>
Co-authored-by: Faisal-imtiyaz123 <142205282+Faisal-imtiyaz123@users.noreply.github.com>
Co-authored-by: Prateek Jain <prateekj1171998@gmail.com>

packages/twenty-front/src/modules/activities/timelineActivities/states/objectShowPageTargetableObjectIdState.ts

@@ -0,0 +1,9 @@
+import { atom } from 'recoil';
+
+import { ActivityTargetableObject } from '@/activities/types/ActivityTargetableEntity';
+
+export const objectShowPageTargetableObjectState =
+  atom<ActivityTargetableObject | null>({
+    key: 'objectShowPageTargetableObjectState',
+    default: null,
+  });