Steps to reproduce:
1. Install CRM, Calendar, and Contacts.
2. Create a contact with an email address you can receive emails on.
3. Configure an outgoing email server.
4. Open a CRM lead and create a meeting activity using the calendar.
5. Add the created contact as an attendee of the meeting.
6. Return to the lead and click the Reschedule button on the activity.
7. Select the same meeting and change its start date to a future date.

Issue:
- Attendees receive the meeting date-change email twice.

Root cause:

- When a calendar event linked to an activity is rescheduled, the event write syncs the new start date to the related activity through `_sync_activities`. That activity write was not marked as calendar-originated after commit https://github.com/odoo/odoo/commit/bc090486bd7810b1b0af1bae398255a2d6615f09, so `mail.activity.write` treated the updated deadline as an activity-originated change and wrote back to the same calendar event.
https://github.com/odoo/odoo/blob/8cbb0fe91a35fcdb4a7e4e1a7e8afe40b1691f11/addons/calendar/models/calendar_event.py#L779
https://github.com/odoo/odoo/blob/8cbb0fe91a35fcdb4a7e4e1a7e8afe40b1691f11/addons/calendar/models/mail_activity.py#L24-L33
- This created a nested calendar event write. Both the nested write and the original write then triggered attendee date-change notifications, resulting in duplicate emails.

Solution:
- Pass the existing `calendar_event_meeting_update` context flag when syncing calendar event changes to linked activities. This prevents the activity sync from writing back to the event while preserving activity-to-event rescheduling.

opw-6209956

Currently, an error will occur when user multi edits name of projects.

Steps to replicate:
- Install `project` and open projects.
- From the list view select multiple projects and edit their name.

Error:
```
File '/home/odoo/src/odoo/saas-19.3/addons/project/models/project_project.py', line 754, in write
    analytic_account_to_update.write({'name': self.name})
File '/home/odoo/src/odoo/saas-19.3/odoo/orm/fields.py', line 1728, in __get__
    record.ensure_one()
File '/home/odoo/src/odoo/saas-19.3/odoo/orm/models.py', line 5341, in ensure_one
    raise ValueError('Expected singleton: %s' % self)
ValueError: Expected singleton: project.project(8, 9, 10)
```

Cause:
- As multiple records were changed at the moment, `self` had multiple recordsets and trying to access `self.name` [1] causes this error.

Solution:
- Avoided accessing `self.name` on a multi-recordset during multi-edit.
- Updated analytic account names using the name recieved in the vals.

[1]: https://github.com/odoo/odoo/blob/a69ec43f490735f639292d116b0207182c5b2581/addons/project/models/project_project.py#L608

sentry-7452096418
---
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Forward-Port-Of: odoo/odoo#267620

Currently, an error will occur when user multi edits name of projects.

Steps to replicate:
- Install `documents_project` and open any project's settings using kebab menu (3 dots).
- Click new > name `Test` > open settings page and unselect `Documents` > Save.
- Click new > name `Test1` > Save.
- From the list view select `Test` and `Test1` and edit their name.

Error:
```
ValueError: Expected singleton: project.project(9, 10)
```

Cause:
- During `multi-edit`, self contains multiple project records.
- When only one of the selected projects has a documents folder (i.e. `use_documents` enabled), `self.documents_folder_id` contains that single folder, making `len(self.documents_folder_id.project_ids) == 1` to be True [1].
- The condition then proceeds to access `self.name` on the `multi-recordset`, raising singleton.

Solution:
- Avoided accessing `self.name` on a `multi-recordset` during multi-edit.
- Filtered projects individually and updated the document folders using the name in vals.

[1]: https://github.com/odoo/enterprise/blob/3c2985ca6011700c271ed14e40e08c89be822753/documents_project/models/project_project.py#L101

sentry-7452096418

Forward-Port-Of: odoo/enterprise#119060