### Issue:
When an employee has a flexible calendar, its gantt view in planning and other modules, like project or time off, shows incorrect grayed-out days. In general, employees with a flexible calendar should not have any grayed out days other than public holidays.

### Steps to reproduce:
- Create a new work schedule:
    - Flexible Hours
    - 24 hours per week
    - 8 average hours per day
- Create an employee with this work schedule
- Open Planning app
- Only the three first days of the week are not grayed out

### Cause:
With 24 hours per week, the worked time can be done in three days. Odoo considers that the first three days of the given time frame are worked, but the others aren't. This result is returned by `_work_intervals_batch()`. In `_unavailable_intervals_batch()` we then build the unavailabilities by taking the inverse of the work intervals. The only exception was for fully flexible resources (i.e. without a calendar).

### Solution:
The case we need to consider is for flexible resources: they are available anytime, all week long except on public holidays and leaves.

To do this we fix the method `_unavailable_intervals_batch()` which is then called by each module. If the resource is flexible, then we only return the interval of the public holidays overlapping with the time frame.

Works in `appointment`, `hr_holiday_gantt`and `project_enterprise`.

In `planning`, we need to skip the case where nothing is returned in `leaves_mapping` otherwise it will consider the `company_leaves` during weeks with no public holiday or leaves.

In `hr_attendances_gantt`, `_unavailable_intervals_batch()` is not called. So we change the way the unavailabilities were computed to call `_unavailable_intervals_batch()` instead.

Forward-Port-Of: odoo/enterprise#109422
Forward-Port-Of: odoo/enterprise#105521

When the "pre fill lot/serial numbers in shopfloor" setting is enabled on the manufacturing operation type, by-products tracked by serial number were incorrectly showing extra empty lines in shopfloor MO cards (both in overview and work center views).

Steps to reproduce:
1. Create a bill of materials for a final product
2. Add a consumable component
3. Create an operation without steps
4. Add a by-product tracked by serial number
5. Specify that the by-product is produced in the operation above
6. In Inventory > Configuration > Operations Types, open the Manufacturing operation type, go to the Traceability section and enable "Pre fill lot/serial numbers in shop floor moves"
7. Create a manufacturing order for the BOM and confirm it
8. Open the Shop Floor view from the MO
9. Observe the extra line for the by-product in both overview and work center views

Root cause:
The visibleMoveLines getter in stock_move.js was showing ALL move lines (including unpicked ones) when picking_type_prefill_shop_floor_lots was enabled, without distinguishing between raw materials/components and by-products. By-products should never show pre-filled lines since users must register them manually by clicking the + button.

Solution:
Modified the visibleMoveLines getter to always filter by-products to show only picked move lines, regardless of the prefill_shop_floor_lots setting. This ensures by-products only display lines that have been explicitly registered by the user, while regular components continue to show pre-filled lines when the setting is enabled.

Task-5431295

Forward-Port-Of: odoo/enterprise#109574
Forward-Port-Of: odoo/enterprise#103260