Add expandable media shelves

[Boanta-C]

What does this PR do?

Adds expandable shelves to the Radarr and Sonarr shelf views. Collapsed shelves keep the existing horizontal scrolling behavior while expanded shelves wrap items into multiple rows so larger groups can be easily browsed.

Type of change

• Bug fix (non-breaking)
• New feature (non-breaking)
• Breaking change (requires a migration plan - see CONTRIBUTING.md golden rule [Feature] Would love Real-Debrid Client support #3)
• Documentation only

Definition of Done checklist

• The feature works end-to-end, tested manually in a running container
• No console.log, dd(), var_dump, TODO, FIXME leftover
• Comments are in English
• Zero credentials in code, commits, logs, or docs
• At least one unit test for new business logic - N/A
• If this is a bug fix: a regression test that reproduces the bug is included - N/A
• make check passes locally
• If an entity was modified: a new migration is committed - N/A
• CHANGELOG.md updated under [Unreleased]
• README.md updated if user-facing behaviour changed - N/A

Notes for the reviewer

Verified:

• Radarr shelves collapse/expand correctly
• Sonarr shelves collapse/expand correctly
• Poster clicks still open details
• Filters/search continue to rebuild shelves correctly
• Other view modes are unaffected

[Shoshuo]

Code looks good, follows the Turbo-safe patterns we use everywhere (onclick = ... instead of addEventListener, var, no const/let). CSS isolated under new classes, CHANGELOG entry under [Unreleased], no console.log, no creds. Tested locally on both Radarr and Sonarr shelves, works as advertised.

Two minor things, not blocking the merge:

• The toggle rebuilds the full shelf on every click (filmsShelfBuilt = false; buildFilmsShelf()), would be slightly nicer to just toggle the is-expanded class. Pure perf, doesn't change UX.
• No tests. Fair enough for pure JS UI, but if you ever come back to this area a Playwright test that opens/collapses a shelf would lock the behaviour in.

Merging this in. Heads-up: I have a v1.1.0 multi-instance refactor sitting on a private mirror that touches films.html.twig and series.html.twig too, so when I push that to GitHub there'll be a small merge conflict on these two files. Nothing on your end to do, I'll resolve it on my side.

Thanks for the first community PR on Prismarr, really appreciated that ! dont hesitate if you want to send more <3