Issue:
In a multi-company environment, when an attachment is uploaded in the chatter, the resulting `ir.attachment` record incorrectly sets the company_id to the current user's default company. This occurs regardless of the active company or the company associated with the record the attachment is linked to.

Steps to reproduce:
In a multi-company setup, activate only Company B. Open any chatter and attach a file.
Navigate to Settings > Technical > Data Structure > Attachments.

Current behaviour:
The created attachment has its company_id set to the user's default company, rather than the currently active company, or the company of the record, even when the record has a company_id field. This behavior introduces inconsistencies in data visibility, particularly when attachments appear to belong to a company different from the one associated with the related business record.

Behaviour After Fix:
If the related record (i.e., the model the attachment is linked to) contains a company_id field, its value will be used as the attachment's company_id otherwise, the attachment's company_id will be set to the currently active company's id.

This logic ensures proper alignment between attachments and their related business records and also maintaining consistency in multi-company scenarios.

task-4563173


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**Problem:**
For an hour-based time off allocation, changing the employee's working schedule leaves the allocation duration (in days) stale, so the balance shown on the Time Off dashboard becomes wrong.

**Steps to reproduce:**
1. Give an employee a working schedule of 8 hours/day.
2. Create an hour-based allocation (time off type with Request Unit = Hours) granting e.g. 8 hours (1 day).
3. Change the employee's working schedule to one with a different Hours per Day (e.g. 4 hours/day).
4. Check the allocation / the Time Off dashboard balance.

**Current behavior:**
number_of_days stays at its old value (1), so the balance is recomputed as 1 day x 4 hours = 4 hours instead of the 8 hours actually accrued.

**Expected behavior:**
The accrued hours stay constant; the duration in days follows the new schedule (8 hours / 4 hours-per-day = 2 days).

**Cause of the issue:**
`number_of_days` and `number_of_hours_display` compute from each other (`number_of_days = number_of_hours_display / hours_per_day` and `number_of_hours_display = number_of_days * hours_per_day`), forming a dependency cycle, and neither depends on the employee's working schedule. So a schedule change never recomputes either field. Adding the schedule to `_compute_number_of_days`' depends does not help: because of the cycle it recomputes `number_of_hours_display` from the stale `number_of_days` first, which silently destroys the accrued hours.

**Fix:**
When the employee's working schedule changes, the accrued hours are the quantity that must be preserved, so the duration is recomputed explicitly from the still-stored `number_of_hours_display` (setting `number_of_days` first, exactly as a manual `_compute_number_of_days()` does). Driving the order by hand is necessary because the cyclic compute graph cannot guarantee `number_of_days` is computed before `number_of_hours_display`.

opw-6276242