Add GET /api/v1/probe endpoint for device inspection

Fast (~1-3s) endpoint that gathers network info about a device
before full stream discovery. Runs ping first, then parallel probes.

Features:
- Ping with ICMP + TCP fallback (works without root)
- Reverse DNS hostname lookup
- ARP table MAC address + OUI vendor identification (2403 entries, 51 camera vendors)
- mDNS HomeKit detection (camera/doorbell, paired status)
- Extensible Prober interface for adding new probe types
- 3-second overall timeout, parallel execution

Response includes "type" field:
- "unreachable" - device not responding
- "standard" - normal IP camera (RTSP/HTTP/ONVIF flow)
- "homekit" - Apple HomeKit camera (PIN pairing flow)

internal/camera/discovery/prober_dns.go

@@ -0,0 +1,36 @@
+package discovery
+
+import (
+	"context"
+	"net"
+	"strings"
+
+	"github.com/eduard256/Strix/internal/models"
+)
+
+// DNSProber performs reverse DNS lookup to find the hostname of a device.
+type DNSProber struct{}
+
+func (p *DNSProber) Name() string { return "dns" }
+
+// Probe performs a reverse DNS lookup on the given IP.
+// Returns nil if no hostname is found (not an error).
+func (p *DNSProber) Probe(ctx context.Context, ip string) (any, error) {
+	resolver := net.DefaultResolver
+
+	names, err := resolver.LookupAddr(ctx, ip)
+	if err != nil || len(names) == 0 {
+		return nil, nil // No hostname found is not an error
+	}
+
+	// LookupAddr returns FQDNs with trailing dot, remove it
+	hostname := strings.TrimSuffix(names[0], ".")
+
+	if hostname == "" {
+		return nil, nil
+	}
+
+	return &models.DNSProbeResult{
+		Hostname: hostname,
+	}, nil
+}