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/model/inbox.go

@@ -0,0 +1,52 @@
+package model
+
+// Inbox represents a channel inbox that groups conversations.
+// Reference: Chatwoot app/models/inbox.rb
+//
+// Chatwoot inbox attributes (permitted_params in InboxesController):
+//
+//	name, avatar, greeting_enabled, greeting_message, enable_email_collect,
+//	csat_survey_enabled, enable_auto_assignment, working_hours_enabled,
+//	out_of_office_message, timezone, allow_messages_after_resolved,
+//	lock_to_single_conversation, portal_id, sender_name_type, business_name,
+//	csat_config (nested hash)
+//
+// Additional Chatwoot fields not in permitted_params but in model:
+//
+//	channel_type, channel_id, account_id, email_address (for email channel),
+//	webhook_url (for API channel), identifier (unique slug)
+type Inbox struct {
+	Base
+	AccountID            uint   `gorm:"index;not null" json:"account_id"`
+	Name                 string `gorm:"size:255;not null" json:"name"`
+	ChannelType          string `gorm:"size:50;index;not null" json:"channel_type"` // web_widget, facebook, twitter, whatsapp, telegram, email, api, etc
+	ChannelID            uint   `gorm:"index;not null" json:"channel_id"`
+	EnableAutoAssignment bool   `gorm:"default:false" json:"enable_auto_assignment"`
+	AutoAssignmentLimit  int    `gorm:"default:0" json:"auto_assignment_limit"`
+	Enabled              bool   `gorm:"default:true" json:"enabled"`
+	ChannelConfig        string `gorm:"type:text" json:"channel_config,omitempty"` // JSON-encoded per-inbox channel configuration
+
+	// Chatwoot inbox settings (from permitted_params)
+	GreetingEnabled            bool   `gorm:"default:false" json:"greeting_enabled"`
+	GreetingMessage            string `gorm:"type:text" json:"greeting_message,omitempty"`
+	EnableEmailCollect         bool   `gorm:"default:true" json:"enable_email_collect"`
+	CsatSurveyEnabled          bool   `gorm:"default:false" json:"csat_survey_enabled"`
+	WorkingHoursEnabled        bool   `gorm:"default:false" json:"working_hours_enabled"`
+	OutOfOfficeMessage         string `gorm:"type:text" json:"out_of_office_message,omitempty"`
+	Timezone                   string `gorm:"size:100" json:"timezone,omitempty"` // e.g. "Asia/Kolkata"
+	AllowMessagesAfterResolved bool   `gorm:"default:true" json:"allow_messages_after_resolved"`
+	LockToSingleConversation   bool   `gorm:"default:false" json:"lock_to_single_conversation"`
+	SenderNameType             string `gorm:"size:50;default:friendly" json:"sender_name_type,omitempty"` // friendly, professional
+	BusinessName               string `gorm:"size:255" json:"business_name,omitempty"`
+	CsatConfig                 string `gorm:"type:text" json:"csat_config,omitempty"` // JSON-encoded CSAT survey configuration
+	AvatarURL                  string `gorm:"size:1024" json:"avatar_url,omitempty"`  // URL to inbox avatar image
+	PortalID                   *uint  `gorm:"index" json:"portal_id,omitempty"`       // FK to help-center portal (nullable)
+
+	// API inbox specific fields
+	WebhookURL string `gorm:"size:1024" json:"webhook_url,omitempty"` // webhook URL for API inboxes
+	Secret     string `gorm:"size:255" json:"secret,omitempty"`       // HMAC secret for API inbox webhook verification
+
+	WorkingHours []WorkingHour `gorm:"foreignKey:InboxID" json:"working_hours,omitempty"`
+}
+
+func (Inbox) TableName() string { return "inboxes" }