fix: technical debts left by the Sites, Authors and SEO slices, plus backend support for the new Sites and Authors pagination

api/router.go

@@ -350,6 +350,7 @@ func NewMediaRouter(container *UseCases, trustedProxies []string) http.Handler {
 	r.Post("/merge", mediaHandler.Merge)
 	r.Patch("/{id}", mediaHandler.Rename)
 	r.Delete("/{id}", mediaHandler.Delete)
+	r.Get("/{id}", mediaHandler.Get)
 	r.Get("/{id}/usage", mediaHandler.Usage)
 	return r
 }