refactor(auth): replace untyped JWT claims with typed Claims struct

Introduced a typed Claims struct in core/auth to replace the raw
map[string]any approach used for JWT claims throughout the codebase.
This provides compile-time safety and better readability when creating,
validating, and extracting JWT tokens. Also upgraded lestrrat-go/jwx
from v2 to v3 and go-chi/jwtauth to v5.4.0, adapting all callers to
the new API where token accessor methods now return tuples instead of
bare values. Updated all affected handlers, middleware, and tests.

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

core/publicurl/publicurl.go

@@ -18,7 +18,7 @@ import (
 // ImageURL generates a public URL for artwork images.
 // It creates a signed token for the artwork ID and builds a complete public URL.
 func ImageURL(req *http.Request, artID model.ArtworkID, size int) string {
-	token, _ := auth.CreatePublicToken(map[string]any{"id": artID.String()})
+	token, _ := auth.CreatePublicToken(auth.Claims{ID: artID.String()})
 	uri := path.Join(consts.URLPathPublicImages, token)
 	params := url.Values{}
 	if size > 0 {