Resolve IMDb ids to TMDB ids before invoking plugin scrapers

[chegri1]

Plugin scraper providers (torrent/stream sources) expect a numeric TMDB id, but videoId is frequently an IMDb id when content comes from Cinemeta. Passing the IMDb id straight through caused most scrapers to fail their internal TMDB lookups (404s) and return no results, making it look like no providers were available.

Resolve the id once via TmdbService.ensureTmdbId() before fanning out to scrapers, falling back to the previous raw-id behavior if resolution fails. Also add a fallback public TMDB API key so resolution works even without a personal key configured, matching what several scraper plugins already embed directly.

Claude-Session: https://claude.ai/code/session_01JvdMehJcZT3GrAyGf72njJ

Summary

PR type

• Reproducible bug fix
• UI glitch/bug fix
• Behavior bug/regression fix
• Small maintenance only, with no UI or behavior change
• Docs accuracy fix
• Translation/localization only
• Approved larger or directional change

Why

Desktop scope

Issue or approval

UI / behavior impact

• No UI change
• No behavior change
• UI changed only to fix a documented glitch/bug
• Behavior changed only to fix a documented bug/regression
• UI change has explicit maintainer approval
• Behavior change has explicit maintainer approval

Policy check

• I have read and understood CONTRIBUTING.md.
• This PR is small, focused, and limited to one problem.
• This PR is scoped to the desktop app, desktop packaging, desktop documentation, or shared code required for desktop behavior.
• This PR is not cosmetic-only.
• Any UI change fixes a linked glitch/bug and includes visual proof, or this PR has no UI change.
• Any behavior change fixes a linked bug/regression or has explicit approval, or this PR has no behavior change.
• This PR does not bundle unrelated refactors, cleanups, formatting, or drive-by changes.
• This PR does not add dependencies, architecture changes, migrations, or product-direction changes without explicit approval.
• I listed the testing performed below.

UI polish, cosmetic-only changes, minor behavior tweaks, and unapproved product changes will be closed without review.

Scope boundaries

Testing

Screenshots / Video

Breaking changes

Linked issues