Add comprehensive mDNS/Bonjour discovery with unified service and diagnostic tools

Features Added:
• mDNS/Bonjour discovery using hashicorp/mdns library
• Unified discovery service combining UPnP + mDNS + configuration
• Parallel discovery execution for optimal performance
• Comprehensive logging for both UPnP and mDNS discovery
• Network diagnostic tools for troubleshooting

New Discovery Methods:
• Configuration-based (fastest, most reliable)
• UPnP/SSDP discovery (widely supported, enhanced logging)
• mDNS/Bonjour discovery (Apple ecosystem friendly)

New Programs & Tools:
• cmd/example-mdns - Standalone mDNS discovery testing
• cmd/example-upnp - Isolated UPnP/SSDP discovery testing
• cmd/mdns-scanner - Network diagnostic tool for mDNS services

Enhanced Build System:
• make dev-mdns / dev-mdns-verbose (mDNS testing)
• make dev-upnp / dev-upnp-verbose (UPnP testing)
• make dev-scan-all (scan all network services)
• make dev-scan-soundtouch (scan for SoundTouch services)

Documentation:
• docs/DISCOVERY.md - Comprehensive discovery guide
• Updated README.md with new features and commands
• Full API documentation and troubleshooting guide

Technical Improvements:
• Detailed request/response logging for UPnP M-SEARCH
• Step-by-step mDNS service discovery tracking
• IP address resolution with IPv4/IPv6 handling
• Service name parsing and device info extraction
• Robust error handling and network diagnostics

Backward Compatibility:
• No breaking changes to existing APIs
• All existing tests pass
• CLI interface unchanged but enhanced
• Legacy UPnP-only service still available

cmd/example-mdns/main.go

@@ -0,0 +1,97 @@
+package main
+
+import (
+	"context"
+	"flag"
+	"fmt"
+	"log"
+	"os"
+	"time"
+
+	"github.com/user_account/bose-soundtouch/pkg/discovery"
+)
+
+func main() {
+	verbose := flag.Bool("v", false, "Enable verbose logging")
+	timeout := flag.Duration("timeout", 5*time.Second, "Discovery timeout")
+	flag.Parse()
+
+	// Configure logging
+	if *verbose {
+		log.SetOutput(os.Stdout)
+		log.SetFlags(log.LstdFlags | log.Lmicroseconds)
+	} else {
+		log.SetOutput(os.Stderr)
+	}
+
+	fmt.Println("SoundTouch mDNS Discovery Example")
+	fmt.Println("================================")
+
+	fmt.Printf("Timeout: %v, Verbose: %v\n", *timeout, *verbose)
+	fmt.Println()
+
+	// Create mDNS discovery service
+	mdnsService := discovery.NewMDNSDiscoveryService(*timeout)
+
+	// Create context with timeout (add buffer time)
+	ctx, cancel := context.WithTimeout(context.Background(), *timeout+2*time.Second)
+	defer cancel()
+
+	fmt.Println("Searching for SoundTouch devices via mDNS...")
+	fmt.Println("This will search for devices advertising _soundtouch._tcp.local. service")
+	if *verbose {
+		fmt.Println("Verbose logging enabled - watch for technical details...")
+	}
+	fmt.Println()
+
+	start := time.Now()
+
+	// Discover devices
+	devices, err := mdnsService.DiscoverDevices(ctx)
+	duration := time.Since(start)
+
+	fmt.Printf("Discovery completed in %v\n", duration)
+	fmt.Println()
+
+	if err != nil {
+		fmt.Printf("mDNS discovery completed with error: %v\n", err)
+		fmt.Println("Note: This might be normal if no devices support mDNS")
+	}
+
+	// Display results
+	if len(devices) == 0 {
+		fmt.Println("No SoundTouch devices found via mDNS")
+		fmt.Println()
+		fmt.Println("Technical Status:")
+		if *verbose {
+			fmt.Println("✓ mDNS query was sent (check logs above for details)")
+			fmt.Println("✓ No network errors during discovery process")
+			fmt.Println("✗ No devices responded with _soundtouch._tcp service")
+		} else {
+			fmt.Println("Run with -v flag for detailed technical information")
+		}
+		fmt.Println()
+		fmt.Println("This could mean:")
+		fmt.Println("- No SoundTouch devices on network")
+		fmt.Println("- Devices don't support Bonjour/mDNS")
+		fmt.Println("- Network blocks multicast traffic (common in corporate networks)")
+		fmt.Println("- Devices use different service name than '_soundtouch._tcp.local.'")
+		return
+	}
+
+	fmt.Printf("Found %d SoundTouch device(s):\n", len(devices))
+	fmt.Println()
+
+	for i, device := range devices {
+		fmt.Printf("%d. %s\n", i+1, device.Name)
+		fmt.Printf("   Host: %s\n", device.Host)
+		fmt.Printf("   Port: %d\n", device.Port)
+		fmt.Printf("   API URL: http://%s:%d/\n", device.Host, device.Port)
+		fmt.Printf("   Location: %s\n", device.Location)
+		fmt.Printf("   Last seen: %s\n", device.LastSeen.Format("2006-01-02 15:04:05"))
+		fmt.Println()
+	}
+
+	fmt.Println("✓ mDNS discovery completed successfully!")
+	fmt.Printf("✓ Found %d device(s) in %v\n", len(devices), duration)
+}