**Description of the issue/feature this PR addresses:**

When adding a custom field (e.g., via Studio) to the Documents list view, clicking the cell directly does not trigger inline edit mode. The user has to first click a standard editable field (like "Owner") to put the row into edit mode before they can modify the custom field.

This occurs because we use a hardcoded whitelist (`editableColumns`) of standard fields allowed to trigger edit mode. Custom fields (`x_`) are missing from this static list.

This commit resolves the issue by dynamically injecting visible, non-readonly custom fields into the `editableColumns` whitelist. This allows user-created fields to be edited inline as expected.

**Steps to reproduce:**

- Documents > Studio > List view > Add any field that accepts user input (e.g. Text/char) > save/exit
- In the same Documents list view > select a row > click the cell belonging to the newly created field > observe that the row does not enter edit mode
- In the same Documents list view > select a row > click a standard editable cell, then click the cell belonging to our newly created field > observe that this then allows us to edit our field

**Current behavior before PR:**

- Custom fields do not trigger inline edit mode

**Desired behavior after PR is merged:**

- Custom fields trigger inline edit mode

opw-6378102

Forward-Port-Of: odoo/enterprise#125378
Forward-Port-Of: odoo/enterprise#125239

## Problem
When dragging the edge of a scheduled workorder to change the start or end time, _web_gantt_move_candidates would throw a traceback. This is because the web call only supplies the new time chosen by the drag+drop. That is, if date_end was changed, date_start wouldn't be present, so accessing the missing field directly triggers a KeyError. This also revealed a secondary issue involving dependent tasks, where if the parent task is rescheduled with the pills, the child task would fail to find candidate reschedule dates (since its only dependency is being moved), and no boundary date would be supplied when calling _web_gantt_reschedule_compute_dates. This led to another traceback.

## Solution
For the first issue, we will get the start date and end date from the supplied values more safely, using get() to default to the original start/end. For the second issue, if the boundary date isn't found by _web_gantt_get_first_and_last_possible_dates, we fall back to the candidate's existing start or end date.

## Steps to replicate (Runbot saas-19.4)
1. Create a product with a BOM with 2 operations on the same workcenter
2. Create an MO for this product, confirm it, and plan it
3. Head to Manufacturing > Planning > Work Orders / Planning
4. Try to change the end date of the first work order by dragging the edge of the pill

opw-6378769

**Problem:**
On a website with rental planning enabled, a customer can book a planning-backed rental product through eCommerce even when no planning resource is free for the requested window. The cart lets them increase the quantity past the available capacity and proceed all the way through checkout without any availability gate.

**Steps to reproduce:**
1. Install `website_sale_renting_planning`.
2. Create a planning role with `sync_shift_rental` and one resource.
3. Create a service product with `rent_ok=True`, `planning_enabled=True` and the role above.
4. Pre-book the resource for some window via a `planning.slot`.
5. From eCommerce, add the product to the cart for the same window.
6. Proceed to checkout/payment.

**Current behavior:**
The cart is considered ready, no warning is shown, and payment can proceed even though no planning resource is free for the chosen period.

**Expected behavior:**
The cart should be flagged as not ready and pre-payment validation should refuse to confirm until the customer picks a different date or quantity.

**Cause of the issue:**
`sale.order._available_dates_for_renting` in `website_sale_renting` is the documented hook for "stock availability" gating of the cart and pre-payment flow (called from `_is_cart_ready` and from `_check_cart_is_ready_to_be_paid`). `website_sale_stock_renting` overrides it to apply a per-line stock check, but
`website_sale_renting_planning` has no such override, so planning-backed rental services reach payment with no availability gate at all.

**Fix:**
Apply the same gating pattern that `website_sale_stock_renting` already uses: override `_available_dates_for_renting` in `website_sale_renting_planning` so that, for each rental line whose product is a planning-synced rentable service, the cart is only considered valid when at least the requested quantity of planning resources is free during the rental window (mirroring the resource and leave filtering already done by `_planning_slot_vals_list_per_sol` at SO confirmation time). This puts the gate at the same point the stock-renting flow enforces it, keeping the public cart/checkout flow consistent across rentable product types.

opw-6247034

Forward-Port-Of: odoo/enterprise#125732
Forward-Port-Of: odoo/enterprise#118943