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

docs/setup/installation.md

@@ -11,7 +11,7 @@ SummerCMS is a Go module. An application requires it, lists its plugins in a `su
 ## Requirements
 
 - Go 1.27.
-- PostgreSQL 16 for any application that uses the data layer. The database's default locale must be the ICU `pl-PL` locale, which lagoon checks when it connects.
+- PostgreSQL 16 for any application that uses the data layer.
 - Docker, only for the integration tests that start PostgreSQL or Mailpit containers.
 
 You do not need Node.js to build an application or these docs. It is needed only when you work on the admin SPA itself.
@@ -74,10 +74,10 @@ summer build
 
 ## Create the database
 
-The commands that touch data open PostgreSQL. Create a database with the locale lagoon checks for:
+The commands that touch data open PostgreSQL. Create a database for the example:
 
 ```sql
-CREATE DATABASE hello TEMPLATE template0 ENCODING 'UTF8' LOCALE_PROVIDER icu ICU_LOCALE 'pl-PL';
+CREATE DATABASE hello;
 ```
 
 ## Configure the application
@@ -117,7 +117,6 @@ From the application directory, `summer migrate`, `summer migrate:status` and `s
 > Known issues in the current framework:
 >
 > - `examples/hello` ships no `http.body_limits` configuration, so `serve` and `route:list` fail with `surf: config http.body_limits.default_bytes is required` until you add `config/http.yaml` as shown above. The same gap makes the example's `TestTypedItemRoute` fail.
-> - lagoon refuses any database whose default locale is not ICU `pl-PL`.
 > - The committed `examples/hello/main.go` is older than what `summer build` generates now, so building the example leaves that file modified. Restore it with `git checkout -- examples/hello/main.go` if you do not intend to commit it.
 
 ## Next steps