feat(lagoon): per-query collation for OrderBy, drop the database locale check

- lagoon.OrderBy takes variadic lagoon.OrderOption values; lagoon.Collate(name)
  emits a validated, double-quoted COLLATE clause (e.g. "pl-x-icu")
- remove the exported CheckLocale and the ICU pl-PL check from Open and Use
- framework test containers and per-test databases are plain PostgreSQL
- lagoon README, root README and docs pages drop the locale requirement;
  queries-and-pagination gains a "Sorting with a collation" section
  backed by ExampleCollate

modules/cabana/auth_test.go

@@ -28,7 +28,6 @@ import (
 	"git.golem15.com/golem15/summercms/modules/party"
 	"git.golem15.com/golem15/summercms/modules/surf"
 	_ "github.com/jackc/pgx/v5/stdlib"
-	"github.com/testcontainers/testcontainers-go"
 	"github.com/testcontainers/testcontainers-go/modules/postgres"
 	"gorm.io/gorm"
 )
@@ -332,9 +331,6 @@ func adminGorm(t *testing.T) *gorm.DB {
 			postgres.WithUsername("cabana"),
 			postgres.WithPassword("cabana"),
 			postgres.BasicWaitStrategies(),
-			testcontainers.WithEnv(map[string]string{
-				"POSTGRES_INITDB_ARGS": "--locale-provider=icu --icu-locale=pl-PL --encoding=UTF8",
-			}),
 		)
 		if err != nil {
 			adminErr = err