CUB-117: Port Moonraker + MQTT printer integrations to Go

- Moonraker REST client with GetPrinterInfo, GetPrintStats, GetPrintHistory
- Moonraker WebSocket client with auto-reconnect + telemetry parsing
- MQTT client via paho.mqtt.golang with TLS support for Bambu Lab
- Moonraker poller worker: background polling, dedup, usage logging to PostgreSQL
- MQTT subscriber worker: Bambu telemetry parsing, print job tracking
- Config: 7 new env vars (MOONRAKER_URL, MQTT_BROKER, etc.)
- main.go: per-printer worker discovery, graceful shutdown

backend/internal/clients/mqtt.go

@@ -0,0 +1,183 @@
+package clients
+
+import (
+	"crypto/tls"
+	"encoding/json"
+	"fmt"
+	"log/slog"
+	"sync"
+	"time"
+
+	mqtt "github.com/eclipse/paho.mqtt.golang"
+)
+
+// ── Bambu Lab telemetry types ───────────────────────────────────────────────
+
+// BambuPrintReport is the JSON payload published by Bambu Lab printers
+// on the MQTT report topic. The structure varies by printer model;
+// we extract the common fields needed for filament tracking.
+type BambuPrintReport struct {
+	// Print holds the active print job data.
+	Print BambuPrintData `json:"print"`
+
+	// VtTray contains AMS tray info; the extruded length is per-tray.
+	VtTray *BambuVtTray `json:"vt_tray,omitempty"`
+}
+
+// BambuPrintData carries the active print state from a Bambu report.
+type BambuPrintData struct {
+	// GcodeFile is the filename being printed.
+	GcodeFile string `json:"gcode_file"`
+	// GcodeState describes the current print state:
+	// "IDLE", "RUNNING", "PAUSE", "FINISH", "FAILED".
+	GcodeState string `json:"gcode_state"`
+	// McPercent is the progress as a percentage (0-100).
+	McPercent int `json:"mc_percent"`
+	// McRemainingTime is the estimated remaining time in minutes.
+	McRemainingTime int `json:"mc_remaining_time"`
+}
+
+// BambuVtTray holds AMS tray telemetry from Bambu printers.
+type BambuVtTray struct {
+	ID         string `json:"id"`
+	TagUID     string `json:"tag_uid"`
+	TrayIDName string `json:"tray_id_name"`
+	// TrayInfoIdx is the hex color code for the tray's filament.
+	TrayInfoIdx string `json:"tray_info_idx"`
+	// TrayColor is a hex color string like "FF0000FF".
+	TrayColor string `json:"tray_color"`
+	// Remain is the percentage of filament remaining on this tray (0-100).
+	Remain int `json:"remain"`
+	// K is a temperature coefficient.
+	K float64 `json:"k"`
+	// N is a second temperature coefficient.
+	N float64 `json:"n"`
+}
+
+// BambuReportHandler is called for each parsed Bambu telemetry message.
+type BambuReportHandler func(report BambuPrintReport) error
+
+// ── MQTT client ─────────────────────────────────────────────────────────────
+
+// MQTTClient wraps the Eclipse Paho MQTT client for Bambu Lab printer
+// telemetry with optional TLS support.
+type MQTTClient struct {
+	broker      string
+	clientID    string
+	topicPrefix string
+	tlsCert     string
+	tlsKey      string
+	handler     BambuReportHandler
+
+	mu     sync.Mutex
+	client mqtt.Client
+}
+
+// MQTTConfig holds the configuration for creating an MQTTClient.
+type MQTTConfig struct {
+	Broker      string // e.g., "ssl://192.168.1.50:8883"
+	ClientID    string // unique MQTT client id, defaults to "extrudex"
+	TopicPrefix string // topic prefix, defaults to "device/+/report"
+	TLSCert     string // path to TLS client certificate (optional)
+	TLSKey      string // path to TLS client key (optional)
+	Handler     BambuReportHandler
+}
+
+// NewMQTTClient creates a new MQTTClient. The connection is not established
+// until Connect is called.
+func NewMQTTClient(cfg MQTTConfig) *MQTTClient {
+	if cfg.ClientID == "" {
+		cfg.ClientID = "extrudex"
+	}
+	if cfg.TopicPrefix == "" {
+		cfg.TopicPrefix = "device/+/report"
+	}
+	return &MQTTClient{
+		broker:      cfg.Broker,
+		clientID:    cfg.ClientID,
+		topicPrefix: cfg.TopicPrefix,
+		tlsCert:     cfg.TLSCert,
+		tlsKey:      cfg.TLSKey,
+		handler:     cfg.Handler,
+	}
+}
+
+// Connect establishes the MQTT connection and subscribes to the configured
+// topic prefix. Returns an error if the initial connection fails.
+func (c *MQTTClient) Connect() error {
+	opts := mqtt.NewClientOptions().
+		AddBroker(c.broker).
+		SetClientID(c.clientID).
+		SetAutoReconnect(true).
+		SetMaxReconnectInterval(30 * time.Second).
+		SetKeepAlive(30 * time.Second).
+		SetPingTimeout(10 * time.Second).
+		SetConnectTimeout(15 * time.Second).
+		SetOnConnectHandler(func(client mqtt.Client) {
+			slog.Info("mqtt: connected", "broker", c.broker)
+			// Subscribe on every reconnect.
+			token := client.Subscribe(c.topicPrefix, 0, c.messageHandler)
+			token.Wait()
+			if err := token.Error(); err != nil {
+				slog.Error("mqtt: subscribe failed on reconnect", "topic", c.topicPrefix, "error", err)
+			} else {
+				slog.Info("mqtt: subscribed", "topic", c.topicPrefix)
+			}
+		}).
+		SetConnectionLostHandler(func(client mqtt.Client, err error) {
+			slog.Warn("mqtt: connection lost", "error", err)
+		})
+
+	// Configure TLS if cert and key are provided.
+	if c.tlsCert != "" && c.tlsKey != "" {
+		cert, err := tls.LoadX509KeyPair(c.tlsCert, c.tlsKey)
+		if err != nil {
+			return fmt.Errorf("mqtt: failed to load TLS cert/key: %w", err)
+		}
+		opts.SetTLSConfig(&tls.Config{
+			Certificates: []tls.Certificate{cert},
+			MinVersion:   tls.VersionTLS12,
+		})
+		slog.Info("mqtt: TLS configured", "cert", c.tlsCert)
+	}
+
+	c.client = mqtt.NewClient(opts)
+	token := c.client.Connect()
+	if !token.WaitTimeout(15 * time.Second) {
+		return fmt.Errorf("mqtt: connect timed out to %s", c.broker)
+	}
+	if err := token.Error(); err != nil {
+		return fmt.Errorf("mqtt: connect failed: %w", err)
+	}
+
+	slog.Info("mqtt: initial connection established", "broker", c.broker)
+	return nil
+}
+
+// Disconnect gracefully closes the MQTT connection.
+func (c *MQTTClient) Disconnect() {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	if c.client != nil && c.client.IsConnected() {
+		c.client.Disconnect(2500) // wait up to 2.5s
+		slog.Info("mqtt: disconnected")
+	}
+}
+
+// messageHandler is the MQTT callback invoked for every message received on
+// the subscribed topic.
+func (c *MQTTClient) messageHandler(_ mqtt.Client, msg mqtt.Message) {
+	if c.handler == nil {
+		return
+	}
+
+	var report BambuPrintReport
+	if err := json.Unmarshal(msg.Payload(), &report); err != nil {
+		slog.Warn("mqtt: failed to parse bambu report", "topic", msg.Topic(), "error", err)
+		return
+	}
+
+	if err := c.handler(report); err != nil {
+		slog.Error("mqtt: handler error", "topic", msg.Topic(), "error", err)
+	}
+}