Return false instead of throwing when event stream does not exist (#20165)

## Summary

- When an event stream expires (TTL), `addQueryToEventStream` and
`removeQueryFromEventStream` now return `false` instead of throwing
`EVENT_STREAM_DOES_NOT_EXIST` as an `InternalServerError`
- Frontend checks the mutation return value and triggers the
destroy/recreate cycle, same recovery behavior without the error path
- Removes `EVENT_STREAM_DOES_NOT_EXIST` from exception code, exception
filter, and frontend graceful error check since it's no longer thrown

## Test plan

- [x] Verify that when an event stream TTL expires, the frontend
silently recreates the stream without error noise in logs/Sentry
- [x] Verify that `NOT_AUTHORIZED` errors still throw correctly on both
mutations
- [ ] Verify that the subscription `onEventSubscription` still works
end-to-end with stream creation, query registration, and heartbeat TTL
refresh

Made with [Cursor](https://cursor.com)

packages/twenty-server/src/engine/subscriptions/event-stream.exception.ts

@@ -7,7 +7,6 @@ import { CustomException } from 'src/utils/custom-exception';
 export enum EventStreamExceptionCode {
   EVENT_STREAM_ALREADY_EXISTS = 'EVENT_STREAM_ALREADY_EXISTS',
   NOT_AUTHORIZED = 'NOT_AUTHORIZED',
-  EVENT_STREAM_DOES_NOT_EXIST = 'EVENT_STREAM_DOES_NOT_EXIST',
 }
 
 const getEventStreamExceptionUserFriendlyMessage = (
@@ -15,7 +14,6 @@ const getEventStreamExceptionUserFriendlyMessage = (
 ) => {
   switch (code) {
     case EventStreamExceptionCode.EVENT_STREAM_ALREADY_EXISTS:
-    case EventStreamExceptionCode.EVENT_STREAM_DOES_NOT_EXIST:
       return msg`Failed to receive real time updates.`;
     case EventStreamExceptionCode.NOT_AUTHORIZED:
       return msg`You are not authorized to perform this action.`;