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>

internal/config/config.go

@@ -9,7 +9,11 @@ import (
 )
 
 type Config struct {
-	Bind string
+	Bind                 string
+	WifiInterface        string
+	UseARPDiscovery      bool
+	DHCPLeasesPath       string
+	ARPTablePath         string
 }
 
 // ConsolidateConfig fills an Options struct by reading configuration from
@@ -19,7 +23,11 @@ type Config struct {
 func ConsolidateConfig() (opts *Config, err error) {
 	// Define defaults options
 	opts = &Config{
-		Bind: ":8080",
+		Bind:            ":8080",
+		WifiInterface:   "wlan0",
+		UseARPDiscovery: true,
+		DHCPLeasesPath:  "/var/lib/dhcp/dhcpd.leases",
+		ARPTablePath:    "/proc/net/arp",
 	}
 
 	declareFlags(opts)