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/lighthouse/postgres_test.go

@@ -58,9 +58,6 @@ func startLighthousePostgres(ctx context.Context) error {
 		postgres.WithUsername("lighthouse"),
 		postgres.WithPassword("lighthouse"),
 		postgres.BasicWaitStrategies(),
-		testcontainers.WithEnv(map[string]string{
-			"POSTGRES_INITDB_ARGS": "--locale-provider=icu --icu-locale=pl-PL --encoding=UTF8",
-		}),
 	)
 	if err != nil {
 		return err
@@ -106,14 +103,14 @@ func adminDB(t *testing.T) *sql.DB {
 	return lhSQL
 }
 
-// migratedDB returns a dedicated ICU pl-PL database migrated with
+// migratedDB returns a dedicated database migrated with
 // lagoon.Migrate (River v7 and summer_jobs) plus its DSN.
 func migratedDB(t *testing.T) (*sql.DB, string) {
 	t.Helper()
 	admin := adminDB(t)
 	ctx := t.Context()
 	name := fmt.Sprintf("lighthouse_%d", dbSeq.Add(1))
-	if _, err := admin.ExecContext(ctx, `CREATE DATABASE `+name+` TEMPLATE template0 ENCODING 'UTF8' LOCALE_PROVIDER icu ICU_LOCALE 'pl-PL'`); err != nil && !strings.Contains(err.Error(), "already exists") {
+	if _, err := admin.ExecContext(ctx, `CREATE DATABASE `+name+` TEMPLATE template0 ENCODING 'UTF8'`); err != nil && !strings.Contains(err.Error(), "already exists") {
 		t.Fatalf("create %s: %v", name, err)
 	}
 	dsn, err := dsnWithDB(lhDSN, name)