Upgrade JQuery dependency to 4.x

[stefannibrasil]

See #6675

[stefannibrasil]

Fixing some CI errors and addressing a code review comment.

[stefannibrasil]

After a few attempts, I couldn't make the app work with jQuery 4.x. bootstrap-select is not compatible with jQuery 4.x. I tried a bunch of things but removing that dependency breaks the search on when generating case reports. So we need to handle that prior to updating jQuery.

I am not super familiar with jQuery to try to add a patch here, but that could be an alternative to finding a replacement to bootstrap-select. Although I imagine patching it would become a problem sooner or later given that the last update was 4 years ago, and finding an alternative that is compatible with jQuery 4 might be better.

cc @FireLemons

[stefannibrasil]

Got a bit far in #6687

[compwron]

Picking up where #6687 left off — I think the upgrade is unblocked once we sequence it differently.

Diagnosis of why #6687 stalled: the conclusion that removing bootstrap-select broke the report search looks like a misattribution. The search-enabled select on the report modal uses select2 (see _generate_docx.html.erb and app/javascript/src/select.js), not bootstrap-select. A grep across app/ finds zero selectpicker class usages — bootstrap-select is genuinely unused. The actual jQuery-4 incompatibilities sit in select2 4.0.13 and bootstrap-datepicker, which is consistent with the lockfile in #6687 carrying a nested jQuery 3.7.1 for bootstrap-datepicker.

Proposed split into independently mergeable PRs:

1. Remove bootstrap-select on its own, while still on jQuery 3. Just drops the import in application.js:5 and the package entry. Smoke-test the report modal — should be a no-op.
2. Migrate select2 → tom-select. Three call sites (src/select.js, casa_case.js:165, reimbursements.js:77) plus the .select2 class on the report template. tom-select is already a dep and is pattern-proven in controllers/multiple_select_controller.js. Drop select2 and select2-bootstrap-5-theme and the @use "select2/dist/css/select2" import. This is the real prerequisite to jQuery 4.
3. Replace bootstrap-datepicker with flatpickr (or another non-jQuery picker). It's the other library that forced the nested-jQuery workaround.
4. Bump jQuery to 4.x. With select2 and bootstrap-datepicker gone, this PR becomes narrow: package bump + addressing @FireLemons's feedback on the jQueryGlobalizer.js hack (use standard ES imports, drop the require('select2')(window.jQuery) and require('datatables.net-dt')(null, window.jQuery) patterns), plus replacing the remaining .tooltip() / .modal() jQuery-plugin calls (tooltip.js:4, case_contact.js:52, dashboard.js:542,648, casa_case.js:194) with the Bootstrap 5 native API.
5. (Optional) Audit whether jQuery is still needed at all. After step 4, datatables-net is the only remaining consumer — and it's jQuery-4-compatible, so this can wait.

Splitting it this way makes each step independently verifiable, and the failure mode that closed #6687 (broken report search) gets handled in step 2 by the migration itself rather than as a side-effect of the jQuery bump.

[stefannibrasil]

Thanks for commenting with actionable steps, @compwron . You're right, I commented on the wrong problem. JQuery is a bit out of my comfort zone and I wanted to see how far I could get.

Extracted the first step of removing bootstrap-select into a new issue: #6929