### Issue
When AI chat is used in views where `config.viewSwitcherEntries` is not initialized, sending a message raises a `TypeError` because the code attempts to call `.map()` on an undefined value.

### Steps to Reproduce
[Video](https://drive.google.com/file/d/1i7kWDnmv4mebGtf1to12BNHCG5omBTXl/view?usp=sharing)
1. Click the **Ask AI** button.
2. Open the AI chat.
3. Keep it open and navigate to the **Shopfloor** app.
4. Send a message in the AI chat.

### Error
```text
TypeError: Cannot read properties of undefined (reading 'map')
    at WithSearch.getCurrentViewInfo
```

### Fix
Safely handle cases where `config.viewSwitcherEntries` is undefined by using optional chaining and falling back to an empty array.

**Before**
```js
result.available_view_types = config.viewSwitcherEntries.map((v) => v.type);
```

**After**
```js
result.available_view_types =
    config.viewSwitcherEntries?.map((v) => v.type) || [];
```

opw-6414684

Forward-Port-Of: odoo/enterprise#126738
Forward-Port-Of: odoo/enterprise#125821

### Issue:
When an invoice has a down payment on a line with a withholding tax, the `PrepaidPayment/PaidAmount` in the UBL XML included the withholding tax amount, causing a mismatch with `LegalMonetaryTotal/PrepaidAmount` which correctly excludes it

### Cause:
`PrepaidPayment/PaidAmount` was set directly from `prepayment_move.amount_total`, which includes all taxes `LegalMonetaryTotal/PrepaidAmount` uses `_aggregate_base_line_tax_details` to exclude withholding taxes, but this was not applied to the `PrepaidPayment` node

### Fix:
Using `prepayment_move.amount_total` directly includes all taxes and does not match the rounding logic of `LegalMonetaryTotal`

Instead, `_aggregate_base_line_tax_details` is used with the same `total_grouping_function` as `LegalMonetaryTotal`, ensuring both nodes use the same rounding logic and exclude withholding taxes

Reversed down payment moves are also excluded from `AdditionalDocumentReference` to avoid referencing cancelled invoices

### Steps to reproduce:
- Install `l10n_pe_edi` and `sale_management` with demo data
- Switch to the PE company
- Create and confirm a Sale Order (Customer: PE Company, Product: Any, Unit Price: 200, Taxes: VAT 18% and 3% IGV Withholding)
- Create, confirm and pay a Down Payment Invoice (Fixed: 28.92)
- Go back to the SO and create the Regular Invoice
- Confirm it and click Process Now
- Open the EDI Document tab and download the XML

Before the fix, the sum of `PrepaidPayment/PaidAmount` did not match `LegalMonetaryTotal/PrepaidAmount`

opw-6273903

Forward-Port-Of: odoo/enterprise#126776
Forward-Port-Of: odoo/enterprise#121733

**Problem:**
When an appointment is cancelled, the cancellation email is always sent in the organizer's (staff member's) language, ignoring the booking customer's language. The booking confirmation, by contrast, is correctly localized.

**Steps to reproduce:**
1. Set a contact's language to a non-default one (e.g. Romanian).
2. Book an appointment for that contact (they are the booker/attendee).
3. Cancel the appointment.
4. The customer received the confirmation in Romanian but the cancellation email arrives in English.

**Current behavior:**
The cancellation email is rendered in the organizer's language.

**Expected behavior:**
The cancellation email is rendered in the booking customer's language, like the confirmation/invitation email.

**Cause of the issue:**
The cancellation uses `appointment_canceled_mail_template`, whose `lang` is `{{ object.partner_id.lang }}`. On `calendar.event`, `partner_id` is `related='user_id.partner_id'`, i.e. the organizer, not the customer. The template is posted once per event (via `_track_template`), so its single rendering language applies to every recipient, including attendees whose own language differs. The confirmation email is unaffected because it is the per-attendee `attendee_invitation_mail_template` (model `calendar.attendee`), rendered once per attendee in that attendee's language.

**Fix:**
Deriving the language from `appointment_booker_id` makes the cancellation consistent with the other appointment mails, which are meant for the person who booked the meeting. It falls back to `partner_id` when there is no booker (e.g. an event not created through the appointment flow), preserving the previous behavior in that case.

opw-6323179

Forward-Port-Of: odoo/enterprise#125927
Forward-Port-Of: odoo/enterprise#124116