feat(12.2-03): add hasMany relation contracts, relation forms and child create

- RelationContract gains Kind (empty is belongsToMany) and ForeignKey, with kind-aware boot checks
- manage.form, view.form and pivot.form compile against the related or pivot model; $/ paths resolve inside the plugin
- view toolbarButtons accept create|update|delete|link|unlink, each the capability of its routes
- POST .../relations/{name}/records creates a child through the manage form; the server sets the hasMany key
- relation schema carries kind, deferrable and the localized forms; 17 new relation message keys in en and pl

modules/cabana/security_coverage_test.go

@@ -62,6 +62,7 @@ var phase09Routes = []adminRoute{
 	{key: "GET /{vendor}/{plugin}/{controller}/{id}/relations/{name}/candidates"},
 	{key: "POST /{vendor}/{plugin}/{controller}/{id}/relations/{name}/link"},
 	{key: "POST /{vendor}/{plugin}/{controller}/{id}/relations/{name}/unlink"},
+	{key: "POST /{vendor}/{plugin}/{controller}/{id}/relations/{name}/records"},
 	{key: "GET /{vendor}/{plugin}/{controller}/{id}/files/{field}", mounted: nestedGetRoute},
 	{key: "POST /{vendor}/{plugin}/{controller}/{id}/files/{field}"},
 	{key: "POST /{vendor}/{plugin}/{controller}/{id}/files/{field}/reorder"},
@@ -293,6 +294,7 @@ func phase09ProtectedCalls() []phase09Call {
 		{"relation-candidates", (*service).relationCandidates},
 		{"relation-link", (*service).relationLink},
 		{"relation-unlink", (*service).relationUnlink},
+		{"relation-child-create", (*service).relationChildCreate},
 		{"file-list", (*service).fileList},
 		{"file-upload", (*service).fileUpload},
 		{"file-reorder", (*service).fileReorder},