refactor(api): enforce protocol-neutral service boundaries

- refactor: move HTTP status and DTO concerns out of model and service
  layers into API and handler code.
- feat: add admin service boundary and route auth through services
  instead of direct repository access.
- test: add architecture and error tests covering package boundaries,
  redaction, and service behavior.
- docs: record the protocol-neutral boundary decision and update
  architecture and roadmap notes.

internal/app/webapp_test.go

@@ -9,7 +9,7 @@ import (
 func TestNewWebApp(t *testing.T) {
 	cfg := &config.Config{}
 
-	webApp := NewWebApp(cfg, nil, nil, nil, nil, nil, nil, nil, nil)
+	webApp := NewWebApp(cfg, nil, nil, nil, nil, nil, nil, nil, nil, nil)
 
 	if webApp.Config != cfg {
 		t.Fatal("Config was not assigned")
@@ -20,7 +20,7 @@ func TestNewWebApp(t *testing.T) {
 }
 
 func TestCloseNilDB(t *testing.T) {
-	webApp := NewWebApp(&config.Config{}, nil, nil, nil, nil, nil, nil, nil, nil)
+	webApp := NewWebApp(&config.Config{}, nil, nil, nil, nil, nil, nil, nil, nil, nil)
 	if err := webApp.Close(); err != nil {
 		t.Errorf("Close with nil DB should not error: %v", err)
 	}