WhatsApp discussion messages now align with the updated way reactions are grouped and shared in the messaging system. This helps keep reaction displays consistent and reliable for users interacting through WhatsApp-related conversations.

Part of task-2828744

Related to odoo/odoo#170553

The Sign app now loads only the default signature font when the signing dialog opens, instead of downloading every available font immediately. This makes the dialog open faster on slower connections, while still loading other font choices in the background when users need them; saved signatures for internal users also appear by default in the draw tab.

Before this commit, when the user opened the sign dialog, all the fonts were downloaded, which could be slow depending on the internet connection.

We decide to use the lightest default font for automatic signature. other fonts are downloaded when the user decide to use another font.

taskid: 3713718

The spreadsheet pivot details side panel has been adjusted to better handle overflowing content. This should make detailed pivot information easier to view and reduce layout issues for users working with spreadsheets.

Event setup and registration processes now avoid unnecessary database work, making common event actions faster. This should improve responsiveness when creating events or handling registrations, without changing business workflows.

Spreadsheets now support a shared default currency setting that can be used for both currency and accounting number formats. This makes financial spreadsheet displays more consistent and easier to configure for business reporting.

Changed the model config `defaultCurrencyFormat` to `defaultCurrency`, so it can be used for both currency and accounting formats.

Task: [4083126](https://www.odoo.com/web#id=4083126&cids=1&menu_id=4720&action=333&active_id=2328&model=project.task&view_type=form)

Spreadsheet filter side panels now use the shared side panel component from the spreadsheet engine instead of a separate Odoo-specific version. This keeps the experience visually consistent while reducing duplicated maintenance work.

After the revamping of the side panels, the component `SidePanelCollapsible` of o-spreadsheet now have the same style as the one we have in Odoo.

We can remove the odoo's implementation and use the one from o-spreadsheet.

Task: [4105418](https://www.odoo.com/web#id=4105418&cids=1&menu_id=4720&action=333&active_id=2328&model=project.task&view_type=form)