Reproduce:
- Switch to mobile view
- Go to Project module
- Click on the gear icon next to a task or project
- Click the Start (or Launch) button in the dropdown
- Try tapping anywhere on the button (not just on the text)

Description of the issue/feature this PR addresses:
In the mobile view of the Project module, clicking the Start button from the dropdown menu only works if the user taps directly on the text. Tapping on the surrounding area within the button does not trigger the action—instead, it closes the menu without starting the timer.

Root cause:
The button inside the dropdown is wrapped in a `<span>` element, but its width does not extend across the entire span. As a result, only the text area is interactive, which causes usability issues on mobile where precise tapping is harder.

Solution:
Ensure the button inside the dropdown item spans the full width of its container by setting `width: 100%`. This allows the entire area of the button to be clickable,  improving usability on mobile devices.

Desired behavior after PR is merged:
Tapping anywhere on the button (not just the text) now consistently triggers the timer as expected.


opw-4561724

Forward-Port-Of: odoo/odoo#205660

Creating many savepoints can lead to issues, not only in the current transaction, but also on other transactions from other connections on other databases[^1].

The `sequence.mixin` relies heavily on a unique constraint for giving a sequence without gaps[^2], which forces the use of savepoints because we expect the transaction to fail when assigning numbers with concurrent transactions.

A previous commit removes savepoints created in a loop, which could happen when concurrency happens[^3], but there is still an issue when many records are getting a sequence number in the same transaction. This happens for instance when posting journal entries in batch (i.e. after an import), creating a `account.asset` in the past, or validating a batch payment with exchange differences.

This commit is now caching the value as soon as the lock is held for a series in the sequence, and is now doing only one savepoint per series in the same transaction.

[^1]: https://github.com/odoo/odoo/pull/71395#issuecomment-851440042
[^2]: c45998c8368c6feb3d574d6d3d0ad064faf21679
[^3]: 10565c6968a5d0f285f93c4bdc610350999a88e3

Forward-Port-Of: odoo/odoo#204510