Add accessible labels and pressed state to Library filter controls

[cmsjade5000]

Goal

Make the Library filter dialog easier to use with assistive technology by giving chip and pill controls explicit names, groups, and state.

During a local UI audit, the filter dialog exposed many generic buttons such as Action, Drama, Any year, Custom, and custom number inputs without enough context. The visible UI works, but screen-reader users should hear what group a control belongs to and whether a filter is selected.

Suggested Scope

• Add accessible grouping/labels around the genre, decade, and runtime filter sections in templates/partials/movies/filter_form.html.
• Add aria-pressed or equivalent state updates for selectable chip/pill buttons in static/js/library_page.js.
• Ensure custom year/runtime fields have stable labels and useful context when revealed.
• Keep the visual design unchanged unless a small CSS tweak is needed for focus states.

Files or Areas

• templates/partials/movies/filter_form.html
• static/js/library_page.js
• static/css/movies.css
• tests/js/library_page.test.js
• tests/test_movies_ui.py

Acceptance Criteria

• Genre, decade, and runtime option buttons expose their selected/unselected state to assistive tech.
• Custom year/runtime number inputs have clear accessible names tied to their filter group.
• Existing filter behavior is unchanged for mouse, touch, and keyboard users.
• Focus styles remain visible in the dialog.
• Add focused JS and/or template tests for the new ARIA/state behavior.

Verification

• npm run test:js
• pytest tests/test_movies_ui.py -k "library_search_is_prominent"
• Optional manual check: open /ui/movies, open Filters, toggle a genre/year/runtime option, and inspect that the pressed state changes.

Contributor Notes

This is a good first issue because it is scoped to one dialog and its small support script. First-time contributors do not need collaborator access or assignment; fork the repo and open a pull request that links this issue. Please use synthetic data only and avoid unrelated UI redesign.