feat(03-01): add shared postgres pool and plugin migrations

Open one pgx stdlib *sql.DB, hand it to GORM, and run per-plugin
gormigrate sets with isolated history tables after an ICU pl-PL check.

Co-authored-by: Cursor <cursoragent@cursor.com>

examples/hello/hello_test.go

@@ -104,6 +104,14 @@ func TestBuiltBinaryGreeterHello(t *testing.T) {
 	assertGreeting(t, got, want)
 }
 
+func TestMigrateWithoutDSNFailsLoudly(t *testing.T) {
+	var buf bytes.Buffer
+	err := run([]string{"migrate"}, &buf)
+	if err == nil || !strings.Contains(err.Error(), "database.dsn") {
+		t.Fatalf("want empty DSN error, got %v\n%s", err, buf.String())
+	}
+}
+
 func TestBuiltBinaryUnknownCommandExitsNonZero(t *testing.T) {
 	runSummerBuild(t)
 	cmd := exec.Command("./bin/hello", "does:not-exist")

examples/hello/main.go

@@ -10,6 +10,7 @@ import (
 	"git.golem15.com/golem15/summercms/backpack"
 	"git.golem15.com/golem15/summercms/bonfire"
 	"git.golem15.com/golem15/summercms/compass"
+	"git.golem15.com/golem15/summercms/lagoon"
 	"git.golem15.com/golem15/summercms/pact"
 	"git.golem15.com/golem15/summercms/party"
 )
@@ -31,7 +32,7 @@ func run(args []string, out io.Writer) error {
 	if err != nil {
 		return err
 	}
-	var commands []bonfire.Command
+	commands := lagoon.RuntimeCommands(app, plugins)
 	for _, plugin := range plugins {
 		if hasCommands, ok := plugin.(pact.HasCommands); ok {
 			commands = append(commands, hasCommands.Commands()...)