refactor: simplify architecture and harden lifecycle

Remove obsolete implementations, centralize background task ownership and terminal-state recovery, consolidate frontend routing and log streaming, and enforce project-wide verification in CI.

server/pkg/response/response_test.go

@@ -0,0 +1,39 @@
+package response
+
+import (
+	"errors"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+
+	"github.com/gin-gonic/gin"
+	"go.uber.org/zap"
+	"go.uber.org/zap/zaptest/observer"
+)
+
+func TestErrorLogsInternalFailureAndHidesDetail(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	recorder := httptest.NewRecorder()
+	ctx, _ := gin.CreateTestContext(recorder)
+	ctx.Request = httptest.NewRequest(http.MethodGet, "/api/test", nil)
+	core, observed := observer.New(zap.WarnLevel)
+	SetLogger(ctx, zap.New(core))
+
+	Error(ctx, errors.New("database password should stay private"))
+
+	if recorder.Code != http.StatusInternalServerError {
+		t.Fatalf("status = %d, want %d", recorder.Code, http.StatusInternalServerError)
+	}
+	if strings.Contains(recorder.Body.String(), "database password") {
+		t.Fatalf("internal detail leaked in response: %s", recorder.Body.String())
+	}
+	entries := observed.All()
+	if len(entries) != 1 || entries[0].Level != zap.ErrorLevel {
+		t.Fatalf("observed logs = %#v, want one error", entries)
+	}
+	context := entries[0].ContextMap()
+	if context["code"] != "INTERNAL_ERROR" || context["path"] != "/api/test" {
+		t.Fatalf("unexpected log context: %#v", context)
+	}
+}