feat: leaderboard collection filter

[gaspergrom]

No description provided.

[Copilot]

Pull request overview

This PR adds a collection filter feature to the leaderboard pages, allowing users to filter leaderboard data by specific collections. The implementation includes a new dropdown filter component with search functionality, backend API support for the collection filter, and an empty state UI for when no results are found.

Key Changes:

• Added collectionSlug query parameter to leaderboard API endpoints for filtering by collection
• Implemented a new LfxCollectionsFilter component with searchable dropdown functionality
• Added search parameter support to the collection API endpoint
• Introduced empty state UI in leaderboard detail view with appropriate messaging

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
frontend/server/api/leaderboard/[type].ts	Added collectionSlug query parameter to filter leaderboard results by collection
frontend/server/api/collection/index.ts	Added search query parameter to enable collection searching
frontend/app/components/modules/leaderboards/services/leaderboard.api.service.ts	Updated query keys and parameters to include collectionSlug for proper cache management
frontend/app/components/modules/leaderboards/components/views/leaderboard-detail.vue	Integrated collection filter, added empty state UI, and adjusted layout styling
frontend/app/components/modules/leaderboards/components/sections/leaderboard-detail-header.vue	Restructured header layout to accommodate collection filter component in both desktop and mobile views
frontend/app/components/modules/leaderboards/components/filters/collections-filter.vue	New component providing searchable dropdown for collection selection
frontend/app/components/modules/collection/services/collections.api.service.ts	Added searchCollections method to fetch collections with search filtering

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