Update ResolveMalId method to accept and process a source parameter, enabling different resolution logic for tmdb and hikka sources. TMDB source now returns null, while HIKKA source uses kinopoiskId when available.
- Add ResolveMalId helper to resolve effective MAL ID from mal_id or kinopoisk_id
- Remove original_title from Search method signature and cache keys
- Simplify BuildSearchUrl to prioritize query parameters (mal_id > imdb_id > title)