chore: sweep example LAN IPs to RFC-5737 in source and config files

Completes the docs-tier RFC-5737 rollout by sweeping the remaining
192.168.1.x references that lived outside .md / .txt / test files:

  - .env.example                                — active PREFERRED_DEVICES default + examples
  - .github/ISSUE_TEMPLATE/*.yml + workflows    — issue template + CI examples
  - cmd/websocket-demo/main.go, doc.go          — top-level docs
  - examples/*/main.go (7 files)                — example program comments
  - pkg/client/client.go                        — godoc examples
  - pkg/models/doc.go                           — package godoc
  - pkg/service/{amazon,spotify,zeroconf}/zeroconf.go — godoc comments
  - pkg/service/handlers/web/index.html         — placeholder text in the UI
  - scripts/prepare-release.sh                  — example invocations
  - scripts/spotify/spotify-prime-speaker.sh    — usage comment
  - tests/integration/http-client/http-client.env.json — fixture IPs

Same mapping as the docs commit (136d24a): 192.168.1.X → 192.0.2.X
preserving the last octet.

One semantic carve-out: the three zeroconf `zcBaseURL` godoc comments
in pkg/service/{amazon,spotify,zeroconf}/zeroconf.go switched to
192.168.10.10 instead of the doc range, because validateZcBaseURL
only accepts RFC-1918 / loopback / link-local. The comment must show
a value the validator actually accepts — see the matching test fix
in 92f66a2 for the same reason.

go build ./... clean. go test ./... clean except the pre-existing
TestDocsConsistency (untracked DEVICE-LOCAL-INSTALL.md, unrelated).
golangci-lint run ./... — 0 issues after a gofmt fix on
examples/zone-slave-operations/main.go.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

examples/account-management/main.go

@@ -13,7 +13,7 @@ import (
 func main() {
 	// Configure the SoundTouch client
 	config := &client.Config{
-		Host:    "192.168.1.100", // Replace with your device IP
+		Host:    "192.0.2.100", // Replace with your device IP
 		Port:    8090,
 		Timeout: 10 * time.Second,
 	}

examples/advanced-audio-controls/main.go

@@ -11,7 +11,7 @@ import (
 
 func main() {
 	// Configure your device
-	deviceIP := "192.168.1.100" // Replace with your SoundTouch device IP
+	deviceIP := "192.0.2.100" // Replace with your SoundTouch device IP
 
 	// Create client
 	soundtouchClient := client.NewClientFromHost(deviceIP)

examples/content-selection/main.go

@@ -163,7 +163,7 @@ func demoLocalMusic(c *client.Client) error {
 	location := "album:983"
 	sourceAccount := "3f205110-4a57-4e91-810a-123456789012" // Example GUID
 	itemName := "Welcome to the New"
-	containerArt := "http://192.168.1.14:8085/v1/albums/983/image"
+	containerArt := "http://192.0.2.14:8085/v1/albums/983/image"
 
 	fmt.Printf("      Album: %s\n", itemName)
 	fmt.Printf("      Location: %s\n", location)
@@ -276,7 +276,7 @@ func printUsage() {
 	fmt.Printf("  %s <device_ip>\n", os.Args[0])
 	fmt.Println()
 	fmt.Println("Example:")
-	fmt.Printf("  %s 192.168.1.100\n", os.Args[0])
+	fmt.Printf("  %s 192.0.2.100\n", os.Args[0])
 	fmt.Println()
 	fmt.Println("Prerequisites:")
 	fmt.Println("• SoundTouch device on your network")

examples/navigation-station-demo/main.go

@@ -239,7 +239,7 @@ func printUsage() {
 	fmt.Printf("  %s <device_ip>\n", os.Args[0])
 	fmt.Println()
 	fmt.Println("Example:")
-	fmt.Printf("  %s 192.168.1.100\n", os.Args[0])
+	fmt.Printf("  %s 192.0.2.100\n", os.Args[0])
 	fmt.Println()
 	fmt.Println("Prerequisites:")
 	fmt.Println("• SoundTouch device on your network")
@@ -247,7 +247,7 @@ func printUsage() {
 	fmt.Println("• Device powered on and connected")
 	fmt.Println()
 	fmt.Println("CLI Equivalent Commands:")
-	fmt.Println("• Browse: soundtouch-cli --host 192.168.1.100 browse tunein")
-	fmt.Println("• Search: soundtouch-cli --host 192.168.1.100 station search-tunein --query jazz")
-	fmt.Println("• Add:    soundtouch-cli --host 192.168.1.100 station add --source TUNEIN --token <token> --name <name>")
+	fmt.Println("• Browse: soundtouch-cli --host 192.0.2.100 browse tunein")
+	fmt.Println("• Search: soundtouch-cli --host 192.0.2.100 station search-tunein --query jazz")
+	fmt.Println("• Add:    soundtouch-cli --host 192.0.2.100 station add --source TUNEIN --token <token> --name <name>")
 }

examples/preset-management/main.go

@@ -378,7 +378,7 @@ func printUsage() {
 	fmt.Printf("  %s <device_ip>\n", os.Args[0])
 	fmt.Println()
 	fmt.Println("Example:")
-	fmt.Printf("  %s 192.168.1.100\n", os.Args[0])
+	fmt.Printf("  %s 192.0.2.100\n", os.Args[0])
 	fmt.Println()
 	fmt.Println("Prerequisites:")
 	fmt.Println("• SoundTouch device on your network")

examples/service-availability/main.go

@@ -16,7 +16,7 @@ func main() {
 	host := getSoundTouchHost()
 	if host == "" {
 		fmt.Println("Usage: go run main.go <soundtouch-host>")
-		fmt.Println("   or: SOUNDTOUCH_TEST_HOST=192.168.1.100 go run main.go")
+		fmt.Println("   or: SOUNDTOUCH_TEST_HOST=192.0.2.100 go run main.go")
 		os.Exit(1)
 	}
 

examples/zone-slave-operations/main.go

@@ -11,7 +11,7 @@ import (
 
 func main() {
 	// Configure your device
-	deviceIP := "192.168.1.100" // Replace with your SoundTouch device IP
+	deviceIP := "192.0.2.100" // Replace with your SoundTouch device IP
 
 	// Create client
 	soundtouchClient := client.NewClientFromHost(deviceIP)
@@ -24,7 +24,7 @@ func main() {
 
 	masterDeviceID := "ABCD1234EFGH" // Replace with actual master device ID
 	slaveDeviceID := "WXYZ5678IJKL"  // Replace with actual slave device ID
-	slaveIP := "192.168.1.101"       // Replace with actual slave IP
+	slaveIP := "192.0.2.101"         // Replace with actual slave IP
 
 	err := soundtouchClient.AddZoneSlave(masterDeviceID, slaveDeviceID, slaveIP)
 	if err != nil {
@@ -117,7 +117,7 @@ func main() {
 	fmt.Println("\n8. Error handling example...")
 
 	// Try to add a non-existent device to demonstrate error handling
-	err = soundtouchClient.AddZoneSlave("INVALID123", "NOTFOUND456", "192.168.1.999")
+	err = soundtouchClient.AddZoneSlave("INVALID123", "NOTFOUND456", "192.0.2.999")
 	if err != nil {
 		fmt.Printf("⚠️  Expected error for invalid operation: %v\n", err)
 		fmt.Println("   This demonstrates proper error handling for invalid device IDs or IPs")