Currently, an error occurs when opening an `accounting report` when the 
evaluated data produces a `zero denominator` during formula computation.

**Steps to reproduce:**
- Install the `account_reports` module (without demo) and enable `developer mode`.
- Navigate to Accounting > Reporting > Deferred Revenue.
- Click the `gear icon` to open the report configuration.
- Click `Add a line` to create a new report line.
- Click `Add a line` to create a new expression with:
>- Computation Engine: `Aggregate Other Formulas`
>- Formula: `0/0`
- Save the new expression and report line.
- Try to reopen the `Deferred Revenue`.

**Error:**
`ZeroDivisionError: division by zero`

**Root Cause:**
After commit [1], at [2], expressions without the `ignore_zero_division` 
subformula are evaluated in the else condition, causing an error when 
the `denominator is zero`.

**Fix:**
This commit prevents errors caused by zero denominators during formula 
evaluation and improves the clarity of the resulting error messages.

[1]:
https://github.com/odoo/enterprise/commit/2ba548564bd0bb68c36a589ed67b43251b5f45d0

[2]:
https://github.com/odoo/enterprise/blob/7adab8bfdccf5f0e97eb2894e065b63ea8200d20/account_reports/models/account_report.py#L3540-L3547

opw-5475146

Forward-Port-Of: odoo/enterprise#103773

When creating a future appointment via the backend, the generated lead's activity deadline is incorrectly set to today instead of the appointment date.

### Steps to reproduce

- Install `appointment_crm`.
- Go to Appointments > Schedule > Staff Booking.
- Create a booking for a future date (e.g., next month) and add a customer.
- Confirm the booking.
- Open the newly created Opportunity.
- Check the "Next Activity" deadline.
- It is set to today's date instead of the appointment's date.

### Cause

The `calendar.event` model maintains two sets of fields for timing: `start`/`stop` (Datetime) and `start_date`/`stop_date` (Date). Standard logic dictates that `start_date` and `stop_date` are only populated for All Day events (`allday=True`). For regular time-specific events, these fields are computed as `False` to avoid ambiguity.

When an appointment is created, `appointment_crm` generates a linked CRM Lead and schedules an activity. The code responsible for scheduling this activity (`activity_schedule`) was explicitly passing `event.start_date` as the `date_deadline`.

Since standard backend appointments are time-specific (not all-day), `event.start_date` is `False`. The `activity_schedule` method defaults to the current date (Today) when it receives a falsy value for the deadline. Consequently, creating a future appointment resulted in an immediate deadline.

### Fix

Modify the lead creation logic to use the standard calendar helper `_get_activity_deadline_from_start`.


opw-5780578

Forward-Port-Of: odoo/enterprise#106162