feat: implement order workflow, metrics, and handler unit tests

- implement UpdateOrderStatus and GetOrdersReport service methods
- implement all order, user handlers (UpdateMe, GetMyTrips, CancelOrder, GetOrder, etc.)
- extract OrderServicer interface for testability
- add Prometheus metrics middleware (requests total, duration)
- fix GetAll storage flavor for PostgreSQL ($1 placeholders)
- add 17 unit tests for order handlers via httptest
- wire Grafana datasource and update Prometheus scrape config
- update README with full API reference, pricing, roles, monitoring

pkg/storage.go

@@ -19,7 +19,7 @@ type Querier interface {
 var ErrNotFound = errors.New("not found")
 
 func GetAll[T any](ctx context.Context, table string, db Querier, opts ...func(*sqlbuilder.SelectBuilder)) ([]T, error) {
-	sb := sqlbuilder.NewStruct(new(T)).SelectFrom(table)
+	sb := sqlbuilder.NewStruct(new(T)).For(sqlbuilder.PostgreSQL).SelectFrom(table)
 
 	sb.From(table)