feat: game templates, schemas and validator

Public game templates for GBR Hosting, one games/<id>/game.yaml per game,
imported from the panel. A Go tool validates them against JSON Schemas and
checks for credentials, private addresses and consents that default to
accepted; CI runs it on every push.

Admin/RCON passwords are no longer shared defaults: they are blank with
x-generate so the panel creates one per server, and Palworld/ARK no longer
publish their RCON/REST ports.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

cmd/gbrgames/main.go

@@ -0,0 +1,34 @@
+// Command gbrgames validates the game templates in this repo and imports them from a panel export.
+//
+//	go run ./cmd/gbrgames validate            # check every games/<id>/game.yaml (+ test.yaml)
+//	go run ./cmd/gbrgames import export.json  # write games/<id>/ from GET /api/v1/admin/games
+package main
+
+import (
+	"fmt"
+	"os"
+)
+
+func main() {
+	if len(os.Args) < 2 {
+		usage()
+	}
+	var err error
+	switch os.Args[1] {
+	case "validate":
+		err = runValidate(os.Args[2:])
+	case "import":
+		err = runImport(os.Args[2:])
+	default:
+		usage()
+	}
+	if err != nil {
+		fmt.Fprintln(os.Stderr, "error:", err)
+		os.Exit(1)
+	}
+}
+
+func usage() {
+	fmt.Fprintln(os.Stderr, "usage: gbrgames validate [-games DIR] | import [-games DIR] [-all] EXPORT.json")
+	os.Exit(2)
+}