feat: add CLI with Cobra and timestamped logging

Introduce structured CLI argument parsing using Cobra with three
configurable flags:
  --vendor: USB vendor ID (default: 0x0fcf)
  --product: USB product ID (default: 0x1008)
  --device: ANT+ device number (default: 3001)

Add timestamped logging for all log statements with format
YYYY-MM-DD HH:MM:SS. Log vendor, product, and device values at
startup in both hex and decimal.

Remove hardcoded USB identifiers from main.go and consolidate all
startup logic into cli.go with a dedicated Config struct.

Update ant.go ListenForTrainer signature to accept uint16 for
vendor and product IDs.

cmd/bridge/ant.go

@@ -26,9 +26,9 @@ func resetAndWait(drv io.ReadWriter) error {
 	}
 }
 
-func ListenForTrainer(vendorId gousb.ID, productId gousb.ID, deviceNumber uint32,
+func ListenForTrainer(vendorId uint16, productId uint16, deviceNumber uint32,
 	events chan<- Event) {
-	drv, err := usb.GetDevice(vendorId, productId)
+	drv, err := usb.GetDevice(gousb.ID(vendorId), gousb.ID(productId))
 	if err != nil {
 		panic(err)
 	}

cmd/bridge/cli.go

@@ -0,0 +1,89 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"strconv"
+
+	"github.com/spf13/cobra"
+)
+
+// Version and BuildTime are injected via ldflags at build time.
+var Version = "unknown"
+var BuildTime = "unknown"
+
+func parseHex(s string, bits int) (uint64, error) {
+	return strconv.ParseUint(s, 0, bits)
+}
+
+type config struct {
+	vendor       string
+	product      string
+	device       string
+	vendorID     uint64
+	productID    uint64
+	deviceNumber uint32
+}
+
+func newConfig() *config {
+	return &config{}
+}
+
+var rootCmd = &cobra.Command{
+	Use:   "bridge",
+	Short: "ANT+ to Bluetooth LE bridge",
+	Long: `Bridge an ANT+ cycling power trainer over Bluetooth Low Energy.
+This allows these trainers to be used with modern devices that don't support ANT+.`,
+	Version: fmt.Sprintf("%s (built %s)", Version, BuildTime),
+	RunE: func(cmd *cobra.Command, args []string) error {
+		c := newConfig()
+
+		c.vendor = cmd.Flags().Lookup("vendor").Value.String()
+		c.product = cmd.Flags().Lookup("product").Value.String()
+		c.device = cmd.Flags().Lookup("device").Value.String()
+
+		vendorID, err := parseHex(c.vendor, 16)
+		if err != nil {
+			return fmt.Errorf("invalid --vendor %q: %w", c.vendor, err)
+		}
+		productID, err := parseHex(c.product, 16)
+		if err != nil {
+			return fmt.Errorf("invalid --product %q: %w", c.product, err)
+		}
+		deviceNumber, err := parseHex(c.device, 32)
+		if err != nil {
+			return fmt.Errorf("invalid --device %q: %w", c.device, err)
+		}
+
+		c.vendorID = vendorID
+		c.productID = productID
+		c.deviceNumber = uint32(deviceNumber)
+
+		logMsgf("ANT Bridge %s built %s", Version, BuildTime)
+		logMsgf("vendor: 0x%04x/%d", vendorID, vendorID)
+		logMsgf("product: 0x%04x/%d", productID, productID)
+		logMsgf("device: 0x%03x/%d", deviceNumber, deviceNumber)
+
+		exec.Command("hciconfig", "hci0", "down").Run()
+		exec.Command("hciconfig", "hci0", "up").Run()
+
+		events := make(chan Event)
+		go ListenForTrainer(uint16(c.vendorID), uint16(c.productID), c.deviceNumber, events)
+		ExposeBluetooth(events)
+
+		return nil
+	},
+}
+
+func init() {
+	rootCmd.Flags().String("vendor", "0x0fcf", "USB vendor ID (hex, e.g. 0x0fcf)")
+	rootCmd.Flags().String("product", "0x1008", "USB product ID (hex, e.g. 0x1008)")
+	rootCmd.Flags().String("device", "3001", "ANT+ device number (hex or decimal, e.g. 3001 or 0xbb9)")
+}
+
+func main() {
+	if err := rootCmd.Execute(); err != nil {
+		os.Exit(1)
+	}
+}

cmd/bridge/log.go

@@ -0,0 +1,18 @@
+package main
+
+import (
+	"fmt"
+	"time"
+)
+
+func logMsg(msg string) {
+	fmt.Println(time.Now().Format("2006-01-02 15:04:05") + " " + msg)
+}
+
+func logPrintf(format string, a ...any) {
+	fmt.Printf(time.Now().Format("2006-01-02 15:04:05")+" "+format, a...)
+}
+
+func logMsgf(format string, a ...any) {
+	logPrintf(format+"\n", a...)
+}

cmd/bridge/main.go

@@ -1,20 +0,0 @@
-package main
-
-import (
-	"os/exec"
-
-	"github.com/google/gousb"
-)
-
-func main() {
-	exec.Command("hciconfig", "hci0", "down").Run()
-	exec.Command("hciconfig", "hci0", "up").Run()
-
-	var vendorId gousb.ID = 0x0fcf
-	var productId gousb.ID = 0x1008
-	var deviceNumber uint32 = 3001
-
-	events := make(chan Event)
-	go ListenForTrainer(vendorId, productId, deviceNumber, events)
-	ExposeBluetooth(events)
-}