Add optional email verification and registration control

Implemented email service infrastructure with SMTP support and optional email verification for self-hosted deployments. Registration flow now supports open/closed modes and hardcoded Apocapoc branding.

Key features:
- Email service with SMTP and template rendering
- Optional email verification (auto-verified without SMTP config)
- Registration modes: open/closed for access control
- Hardcoded Apocapoc branding (AppName, AppURL, DefaultFrom)
- Separate registration and login flows (registration no longer returns tokens)

internal/infrastructure/http/integration_test.go

@@ -41,7 +41,7 @@ func setupTestServer(t *testing.T) *TestServer {
 	entryRepo := sqlite.NewHabitEntryRepository(db)
 	refreshTokenRepo := sqlite.NewRefreshTokenRepository(db)
 
-	registerHandler := commands.NewRegisterUserHandler(userRepo, passwordHasher)
+	registerHandler := commands.NewRegisterUserHandler(userRepo, passwordHasher, nil, "", "open")
 	loginHandler := queries.NewLoginUserHandler(userRepo, passwordHasher)
 	refreshTokenHandler := queries.NewRefreshTokenHandler(refreshTokenRepo, userRepo)
 	revokeTokenHandler := commands.NewRevokeTokenHandler(refreshTokenRepo)
@@ -104,3 +104,22 @@ func decodeResponse(t *testing.T, rr *httptest.ResponseRecorder, target interfac
 		t.Fatalf("Failed to decode response: %v", err)
 	}
 }
+
+func registerAndLogin(t *testing.T, router http.Handler, email, password string) string {
+	registerBody := RegisterRequest{
+		Email:    email,
+		Password: password,
+		Timezone: "UTC",
+	}
+	makeRequest(t, router, "POST", "/api/v1/auth/register", registerBody, "")
+
+	loginBody := LoginRequest{
+		Email:    email,
+		Password: password,
+	}
+	rr := makeRequest(t, router, "POST", "/api/v1/auth/login", loginBody, "")
+
+	var authResp AuthResponse
+	decodeResponse(t, rr, &authResp)
+	return authResp.Token
+}