feat(iot): Этапы 2-7 — MQTT auth, IoT API, EMQX, mqtt-bridge, E2E demo

Этап 2+4: internal/api/handler/iot_device_handler.go
  - MQTTAuth: POST /internal/mqtt/auth (без JWT, для EMQX)
  - CreateIoTDevice, ListIoTDevices, GetIoTDevice (c password), DeleteIoTDevice, UpdateIoTDevice
  - crypto/subtle.ConstantTimeCompare против timing attacks

Этап 4: internal/api/router.go
  - /v1/namespaces/{ns}/iot/devices CRUD
  - /internal/mqtt/auth (без JWT middleware)

Этап 3: deployments/k8s/emqx.yaml
  - EMQX 5.5.1, emqx.conf (HOCON) с HTTP auth backend
  - Сервис exposure: 1883 (MQTT), 8083 (WS), 18083 (Dashboard)

Этап 3: iot/cmd/mqtt-bridge/main.go
  - paho.mqtt.golang: подписка на +/telemetry/+
  - amqp091-go: publish в iot.{namespace}.telemetry
  - deployments/k8s/iot-mqtt-bridge.yaml

Этап 7: examples/IOT/ — E2E demo (main.tf, handler.py, README.md)

go.mod: добавлен github.com/eclipse/paho.mqtt.golang v1.5.1
go build ./... — ошибок нет

go.mod

@@ -19,6 +19,7 @@ require (
 	github.com/cespare/xxhash/v2 v2.1.2 // indirect
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/dustin/go-humanize v1.0.1 // indirect
+	github.com/eclipse/paho.mqtt.golang v1.5.1 // indirect
 	github.com/emicklei/go-restful/v3 v3.9.0 // indirect
 	github.com/evanphx/json-patch/v5 v5.6.0 // indirect
 	github.com/fsnotify/fsnotify v1.6.0 // indirect
@@ -35,6 +36,7 @@ require (
 	github.com/google/go-cmp v0.5.9 // indirect
 	github.com/google/gofuzz v1.1.0 // indirect
 	github.com/google/uuid v1.6.0 // indirect
+	github.com/gorilla/websocket v1.5.3 // indirect
 	github.com/imdario/mergo v0.3.6 // indirect
 	github.com/josharian/intern v1.0.0 // indirect
 	github.com/json-iterator/go v1.1.12 // indirect
@@ -65,6 +67,7 @@ require (
 	golang.org/x/crypto v0.46.0 // indirect
 	golang.org/x/net v0.48.0 // indirect
 	golang.org/x/oauth2 v0.0.0-20220223155221-ee480838109b // indirect
+	golang.org/x/sync v0.19.0 // indirect
 	golang.org/x/sys v0.39.0 // indirect
 	golang.org/x/term v0.38.0 // indirect
 	golang.org/x/text v0.32.0 // indirect