fix(api): add TMDB ID enrichment for KP content via IMDB ID lookup

- Add TMDBID field to ExternalIDs model
- Enhance GetExternalIDs in MovieService and TVService to fetch TMDB ID via FindTMDBIdByIMDB
- Add EnrichKPWithTMDBID function to enrich unified content with TMDB IDs
- Update unified handlers to automatically enrich KP content with TMDB IDs
- Enrich search results with TMDB IDs by fetching full film data for each result

This ensures that when using source=kp, the response includes TMDB IDs in externalIds
when available through IMDB ID mapping, while preserving all original KP data.

pkg/models/movie.go

@@ -123,6 +123,7 @@ type ExternalIDs struct {
 	ID          int    `json:"id"`
 	IMDbID      string `json:"imdb_id"`
 	KinopoiskID int    `json:"kinopoisk_id,omitempty"`
+	TMDBID      int    `json:"tmdb_id,omitempty"`
 	TVDBID      int    `json:"tvdb_id,omitempty"`
 	WikidataID  string `json:"wikidata_id"`
 	FacebookID  string `json:"facebook_id"`