Add configuration system and ARP-based device discovery

Implement comprehensive configuration management with CLI flags for WiFi interface, device discovery method, and file paths. Add ARP table parsing as an alternative to DHCP leases for more reliable device detection. Improve WiFi scanning to handle concurrent scan requests gracefully.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

cmd/repeater/main.go

@@ -25,7 +25,7 @@ func main() {
 	application := app.New(assets)
 
 	// Initialize the application
-	if err := application.Initialize(); err != nil {
+	if err := application.Initialize(cfg); err != nil {
 		log.Fatalf("Failed to initialize application: %v", err)
 	}
 	defer application.Shutdown()