Reorganize repo: backend/, deploy/, docs/ layout + AGENTS.md

Restructure the monorepo into clear top-level directories:
- backend/: Go module root (cmd, internal, pkg, configs, migrations,
  docs/swagger, scripts, tests, go.mod, Makefile, .air.toml)
- deploy/: Docker (Dockerfile, docker-compose*), quickstart, fluentd
- docs/: project documentation + reports/ (moved from repo root)
- AGENTS.md: new AI coding-agent guide at repo root

Update all references to the new layout:
- Dockerfile: COPY backend/go.mod, COPY backend/ (context = repo root)
- docker-compose files: context ../.., dockerfile deploy/docker/Dockerfile,
  env_file ../../.env, volume mounts ../../backend:/app
- deploy/quickstart/compose.yaml: dockerfile deploy/docker/Dockerfile
- CI: working-directory: backend for go commands, file deploy/docker/Dockerfile,
  coverage path backend/coverage.out, health_check backend/scripts/
- backend/Makefile: docker target uses -f ../deploy/docker/Dockerfile ../
- README: architecture tree, quickstart, config paths updated

Move root stray scripts (rename_models.*, run_m11_tests.sh, verify_build.sh,
gorm_bool_main.go) to backend/scripts/legacy/. All moves via git mv to
preserve history. Build, vet, SQLite tests, and docker compose config verified.

backend/internal/handler/api/v1/widget_test_handler.go

@@ -0,0 +1,59 @@
+package v1
+
+import (
+	"net/http"
+
+	"github.com/gin-gonic/gin"
+
+	"github.com/gochat/gochat/internal/service"
+	"github.com/gochat/gochat/pkg/response"
+)
+
+// WidgetTestHandler handles read-only WidgetTest endpoints (platform scope, super-admin).
+// Reference: Chatwoot resources :widget_tests, only: [:index] — not available in production.
+// Returns test data for widget/UI integration testing.
+type WidgetTestHandler struct {
+	svc *service.WidgetTestService
+}
+
+// NewWidgetTestHandler creates a new WidgetTestHandler with service injection.
+func NewWidgetTestHandler(svc *service.WidgetTestService) *WidgetTestHandler {
+	return &WidgetTestHandler{svc: svc}
+}
+
+// Index retrieves all widget test scenarios (list all).
+// GET /platform/api/v1/widget_tests
+func (h *WidgetTestHandler) Index(c *gin.Context) {
+	tests, err := h.svc.List(c.Request.Context())
+	if err != nil {
+		handleServiceError(c, err)
+		return
+	}
+	response.OK(c, tests)
+}
+
+// ListByType retrieves widget test scenarios filtered by type.
+// GET /platform/api/v1/widget_tests/:type
+func (h *WidgetTestHandler) ListByType(c *gin.Context) {
+	typ := c.Param("type")
+	if typ == "" {
+		response.AbortWithStatusError(c, http.StatusBadRequest, response.ErrBadRequest, "type parameter is required")
+		return
+	}
+	tests, err := h.svc.ListByType(c.Request.Context(), typ)
+	if err != nil {
+		handleServiceError(c, err)
+		return
+	}
+	response.OK(c, tests)
+}
+
+// RegisterWidgetTestRoutes registers widget_test routes on a Gin router group.
+// Reference: Chatwoot resources :widget_tests, only: [:index] — platform scope (super-admin).
+func RegisterWidgetTestRoutes(g *gin.RouterGroup, h *WidgetTestHandler) {
+	widgetTests := g.Group("/widget_tests")
+	{
+		widgetTests.GET("/", h.Index)
+		widgetTests.GET("/:type", h.ListByType)
+	}
+}