Fix AI chat streaming persistence when command menu closes (#14854)

Closes [#1583](https://github.com/twentyhq/core-team-issues/issues/1583)


- Removed `messageId` column from `File` table and its references in
code (unrelated to this PR)
- Updated AI chat to use React Context API with persistent provider in
`CommandMenuContainer`
- Converted all AI chat component states to regular Recoil atoms (no
instance context needed)

---------

Co-authored-by: Félix Malfait <felix@twenty.com>

packages/twenty-front/src/modules/ai/states/currentAIChatThreadState.ts

@@ -0,0 +1,6 @@
+import { atom } from 'recoil';
+
+export const currentAIChatThreadState = atom<string | null>({
+  key: 'ai/currentAIChatThreadState',
+  default: null,
+});