T56: Metadata: TVDB/TMDB direct, scene numbering, XEM

[thedancingdeveloper]

Skyhook is Sonarr-operated infrastructure we cannot use. Going direct means API keys, differing data shapes, and — critically — scene numbering and XEM mapping, where naive rewrites break and never recover.

Budget as a project in itself.

Acceptance: scene-numbered series resolve correctly against a known-hard fixture set.

[thedancingdeveloper]

🤖 Vogt validation pass — 2026-08-20 (automated review vs dd26a0aa)

Valid and still pending. crates/stackarr-metadata/src/lib.rs implements only a TmdbClient (TVDB appears solely as an external-id lookup passed through TMDB, tvdb_id field); there is no direct TVDB client and no XEM/scene-mapping engine anywhere in crates (xem occurs only in plan docs and unrelated cardigann/nzb files). scene_* columns exist on the media model but no resolution logic populates or maps them, so scene-numbered series resolution against a hard fixture set is not yet built.