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/service/conversation_delete_worker.go

@@ -0,0 +1,40 @@
+package service
+
+import (
+	"context"
+	"encoding/json"
+	"sync"
+
+	"github.com/gochat/gochat/internal/model"
+	"github.com/gochat/gochat/internal/worker"
+)
+
+const TaskTypeConversationDeleteObject = "conversation:delete_object"
+
+type conversationDeleteObjectJob struct {
+	AccountID      uint `json:"account_id"`
+	ConversationID uint `json:"conversation_id"`
+}
+
+var conversationDeleteRegistrations sync.Map
+
+// RegisterConversationDeleteJobs wires Chatwoot's DeleteObjectJob path for
+// conversation destroy actions. Without a worker, ConversationService.Delete
+// keeps the synchronous fallback used by focused tests.
+func RegisterConversationDeleteJobs(wp *worker.WorkerPool, svc *ConversationService) {
+	if wp == nil || svc == nil {
+		return
+	}
+	if _, loaded := conversationDeleteRegistrations.LoadOrStore(wp, struct{}{}); loaded {
+		return
+	}
+	wp.Register(TaskTypeConversationDeleteObject, svc.performConversationDeleteObject)
+}
+
+func (s *ConversationService) performConversationDeleteObject(ctx context.Context, job *model.BackgroundJob) error {
+	var payload conversationDeleteObjectJob
+	if err := json.Unmarshal(job.Payload, &payload); err != nil {
+		return err
+	}
+	return s.deleteNow(ctx, payload.AccountID, payload.ConversationID)
+}