Fix featured activities filters (malformed component markup)

[bernardhanna]

Summary

• Repair the malformed markup in livewire/online-calendar.blade.php: a stray </div> closed <section>, leaving the component without valid nesting
• Move language-code normalisation onto Event as display_languages / normalizeLanguageCode, so cards no longer print base.languages.eng
• Reuse that helper in OnlineCalendar instead of a duplicate private copy

Root cause

Filters were reaching the server and returning correct data. Verified live: after changing the month, the Livewire response contained Showing 199 of 209 while the DOM still showed Showing 209 of 209, and wire:snapshot never advanced past all.

The cause is invalid HTML in the component view:

<section class="relative w-full pt-10 md:pt-32">
  ...
</div>   <-- stray, closes the section instead
</section>

The browser re-nests this into a different tree than the server rendered, so Livewire's morph cannot match nodes and silently leaves the DOM untouched. Pagination still worked because it navigates via URL rather than morphing.

This explains why removing the duplicate Livewire script and Alpine v2 did not fix filtering: those were real problems, but this one was underneath them.

Test plan

• Hard refresh /featured-activities
• Change Month and confirm the list and the "Showing X of Y" line update
• Change Language and confirm filtering applies, including the empty state
• Confirm no card shows base.languages.*
• Confirm pagination still works and resets when a filter changes

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