add get cities handler and improve db schema

service_a/internal/domains/meteo/handlers.go

@@ -79,6 +79,7 @@ func (h *Handler) IngestExcel(w http.ResponseWriter, r *http.Request) {
 }
 
 func (h *Handler) GetCities(w http.ResponseWriter, r *http.Request) {
+	h.ToJSON(w, http.StatusOK, app.H{"cities": h.s.GetCities(r.Context())})
 }
 
 func (h *Handler) GetMeteoData(w http.ResponseWriter, r *http.Request) {