feat(season): season poster support

[PNRxA]

Summary

Adds season poster support — a TV season's own poster (2:3) rendered with rating badges — motivated by the Plex metadata provider, which can now request per-season art instead of falling back to the show poster.

New endpoint:

GET /{api_key}/{id_type}/season-default/{id_value}    (+ /c/ CDN variant)

with a season-{show}-S{n} id for all three id types:

ID type	Example
TMDB	season-default/season-1396-S2.jpg
IMDb	season-default/season-tt0903747-S2.jpg
TVDB	season-default/season-81189-S2.jpg

The id is the series id combined with the season number (mirrors the existing episode-{id}-S{n}E{n} convention).

What's included

ID resolution (id/mod.rs) — MediaType::Season, SeasonInfo, season-{id}-S{n} parsers + resolvers for imdb/tmdb/tvdb. Seasons carry no imdb id of their own, so the show's imdb/tvdb id is resolved for downstream ratings; poster_path is the season poster with a series-poster fallback.

Rendering — seasons reuse the existing 2:3 poster pipeline (generate_poster). New handle_season_inner / generate_season_with_source / try_fanart_path_season / trigger_season_refresh mirror the poster handlers. A dedicated ImageType::Season (seasons/ subdir, _s cache prefix, db value s) keeps caches fully isolated from series posters.

Ratings — season-scoped where the source supports it: TMDB (the season's vote_average) and Trakt (the season rating). IMDb / RT / Metacritic fall back to show-level (via the show imdb id); MDBList is skipped (no season endpoint).

Art sources — Fanart.tv seasonposter (filtered by season number, with an all fallback) → TMDB season poster → series poster. Language/textless variants work as for posters.

Settings + admin UI — 8 dedicated season_* render settings mirroring the poster controls (ratings limit, badge style/label/size/position/direction/shape/background; no blur/fit/split). New DB columns + migrations (defaults match the code defaults), per-key + global settings, free-key settings, and a full Seasons admin page (SeasonsView, settings form, sidebar nav, preview).

Docs — README season endpoint section, URL templates, cache/db tables, and OpenAPI getSeason.

Testing

• cargo test — 0 failures (494 lib tests + all integration suites; new season tests across db_operations, query_overrides, image_size, cdn_redirects, plus id-resolution + fanart unit tests).
• cargo build --release --features test-support — clean.
• Frontend vitest — 340 passing (27 files); build-only — clean.
• An adversarial multi-dimension review (cache-key collisions, serve pipeline, id/ratings/fanart, settings/migrations, routing/contract) confirmed 0 defects.

Follow-up (separate repo)

openposterdb-plex-provider should map Plex type 3 (season) items to this endpoint (Kind::Season(n) → season-{base}-S{n}, season-default) instead of returning the show poster. The Jellyfin plugin could add season images similarly. No change needed in this repo.

🤖 Generated with Claude Code