feat(discover): add TMDB List slider support

[yannskee]

Implements TMDB List slider type allowing admins to create custom discovery sliders from public TMDB lists.

• Add TMDB List API integration (getList method)
• Add TMDB_LIST slider type to DiscoverSliderType enum
• Create /api/v1/discover/tmdb-list/:listId endpoint
• Add UI for creating and displaying TMDB List sliders
• Add dedicated list view page at /discover/tmdb-list/:id
• Update OpenAPI spec with new route definition
• Add Cypress e2e test for TMDB List slider creation

Closes https://github.com/sct/overseerr/discussions/4270

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