Add course audience tag filter for frontpage and archive

[jensjvh]

Description

What?

Add a dropdown for filtering courses by their tag (currently Aalto, MOOC, Aalto and MOOC) on the front page and archive views.

Why?

[ANSWER HERE]

How?

JavaScript filter with the tag choices hard coded.

Implements #580

Testing

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• Accessibility test using the WAVE extension.
• Django unit tests.
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• Other test. (Add a description below)
• Manual testing.

[ADD A DESCRIPTION ABOUT WHAT YOU TESTED MANUALLY]

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Translation

• Did you modify or add new strings in the user interface? (Read about how to create translation)

Programming style

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Is it Done?

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[jensjvh]

Right now this is very hard coded, and would probably need to be refactored if many new course tags are added. Let me know if you have a better idea on how to do this.

[Copilot]

Pull request overview

Adds a client-side “course audience” (enrollment audience) filter UI to the course front page and course archive views, allowing users to quickly narrow visible course cards by audience tag.

Changes:

• Add a dropdown checkbox filter UI (“Filter courses”) to index and archive pages.
• Expose enrollment audience choices and labels to templates and annotate course cards with data-audience.
• Implement the filtering logic in a new JS file and add the related i18n strings.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
locale/fi/LC_MESSAGES/django.po	Adds Finnish translation for the new filter UI label (and updates POT metadata/wrapping).
locale/en/LC_MESSAGES/django.po	Adds English translation for the new filter UI label (and updates POT metadata/wrapping).
course/views.py	Provides course_tag_choices and audience labels to the front page and archive templates.
course/templates/course/index.html	Includes the new filter UI on the front page.
course/templates/course/archive.html	Includes the new filter UI alongside the search on the archive page.
course/templates/course/_filter_courses_form.html	New partial for the dropdown checkbox filter and script include.
course/templates/course/_course_cards.html	Adds data-audience attribute to course cards for JS filtering.
course/static/course/course_filter.js	New client-side logic to show/hide cards based on selected audiences.

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[ihalaij1]

Great!

This implementation is good enough for now. It can be improved later if we decide to add more course tags.