feat: add ISRC matching for similar songs (#4946)

* feat: add ISRC support to similar songs matching and plugin interface

Add ISRC (International Standard Recording Code) as a high-priority
identifier in the provider matching algorithm, alongside MBID. The
matching pipeline now uses four strategies in priority order:
ID > MBID > ISRC > Title+Artist fuzzy match.

- Add ISRC field to agents.Song struct
- Add ISRC field to plugin capability SongRef (Go, Rust PDKs)
- Add loadTracksByISRC using json_tree query on tags column
- Integrate ISRC into matchSongsToLibrary, selectBestMatchingSongs,
  and buildTitleQueries

https://claude.ai/code/session_01Dd4mTq1VQZag4RNjCVusiF

* chore: regenerate plugin schema after ISRC addition

Run `make gen` to update the generated YAML schema for the
metadata agent capability with the new ISRC field on SongRef.

https://claude.ai/code/session_01Dd4mTq1VQZag4RNjCVusiF

* feat(mediafile): add GetAllByTags method to MediaFileRepository for tag-based retrieval

Signed-off-by: Deluan <deluan@navidrome.org>

* feat(provider): speed up track matching by incorporating prior matches in ISRC and MBID lookups

Signed-off-by: Deluan <deluan@navidrome.org>

---------

Signed-off-by: Deluan <deluan@navidrome.org>
Co-authored-by: Claude <noreply@anthropic.com>

persistence/mediafile_repository.go

@@ -195,6 +195,31 @@ func (r *mediaFileRepository) GetAll(options ...model.QueryOptions) (model.Media
 	return res.toModels(), nil
 }
 
+func (r *mediaFileRepository) GetAllByTags(tag model.TagName, values []string, options ...model.QueryOptions) (model.MediaFiles, error) {
+	placeholders := make([]string, len(values))
+	args := make([]any, len(values))
+	for i, v := range values {
+		placeholders[i] = "?"
+		args[i] = v
+	}
+	tagFilter := Expr(
+		fmt.Sprintf("exists (select 1 from json_tree(media_file.tags, '$.%s') where key='value' and value in (%s))",
+			tag, strings.Join(placeholders, ",")),
+		args...,
+	)
+
+	var opts model.QueryOptions
+	if len(options) > 0 {
+		opts = options[0]
+	}
+	if opts.Filters != nil {
+		opts.Filters = And{tagFilter, opts.Filters}
+	} else {
+		opts.Filters = tagFilter
+	}
+	return r.GetAll(opts)
+}
+
 func (r *mediaFileRepository) GetCursor(options ...model.QueryOptions) (model.MediaFileCursor, error) {
 	sq := r.selectMediaFile(options...)
 	cursor, err := queryWithStableResults[dbMediaFile](r.sqlRepository, sq)