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/probe.go

@@ -0,0 +1,180 @@
+package discovery
+
+import (
+	"context"
+	"sync"
+	"time"
+
+	"github.com/eduard256/Strix/internal/models"
+)
+
+const (
+	// ProbeTimeout is the overall timeout for all probes combined.
+	ProbeTimeout = 3 * time.Second
+
+	// ProbeTypeUnreachable indicates the device did not respond to ping.
+	ProbeTypeUnreachable = "unreachable"
+	// ProbeTypeStandard indicates a normal IP camera (RTSP/HTTP/ONVIF).
+	ProbeTypeStandard = "standard"
+	// ProbeTypeHomeKit indicates an Apple HomeKit camera that needs PIN pairing.
+	ProbeTypeHomeKit = "homekit"
+)
+
+// Prober is an interface for network probe implementations.
+// Each prober discovers specific information about a device at a given IP.
+// New probers can be added by implementing this interface and registering
+// them with ProbeService.
+type Prober interface {
+	// Name returns a unique identifier for this prober (e.g., "dns", "arp", "mdns").
+	Name() string
+	// Probe runs the probe against the given IP address.
+	// Must respect context cancellation/timeout.
+	// Returns nil result if nothing was found (not an error).
+	Probe(ctx context.Context, ip string) (any, error)
+}
+
+// ProbeService orchestrates multiple probers to gather information about a device.
+// It first pings the device, then runs all registered probers in parallel.
+type ProbeService struct {
+	pinger  *PingProber
+	probers []Prober
+	logger  interface {
+		Debug(string, ...any)
+		Error(string, error, ...any)
+		Info(string, ...any)
+	}
+}
+
+// NewProbeService creates a new ProbeService with the given probers.
+// The ping prober is always included and runs first.
+func NewProbeService(
+	probers []Prober,
+	logger interface {
+		Debug(string, ...any)
+		Error(string, error, ...any)
+		Info(string, ...any)
+	},
+) *ProbeService {
+	return &ProbeService{
+		pinger:  &PingProber{},
+		probers: probers,
+		logger:  logger,
+	}
+}
+
+// Probe runs ping + all registered probers against the given IP.
+// Overall timeout is 3 seconds. Results are collected from whatever
+// finishes in time; slow probers are omitted (nil in response).
+func (s *ProbeService) Probe(ctx context.Context, ip string) *models.ProbeResponse {
+	ctx, cancel := context.WithTimeout(ctx, ProbeTimeout)
+	defer cancel()
+
+	response := &models.ProbeResponse{
+		IP:   ip,
+		Type: ProbeTypeStandard,
+	}
+
+	// Step 1: Ping
+	s.logger.Debug("probing device", "ip", ip)
+
+	pingResult, err := s.pinger.Ping(ctx, ip)
+	if err != nil || !pingResult.Reachable {
+		errMsg := "device unreachable"
+		if err != nil {
+			errMsg = err.Error()
+		}
+		s.logger.Debug("ping failed", "ip", ip, "error", errMsg)
+		response.Reachable = false
+		response.Type = ProbeTypeUnreachable
+		response.Error = errMsg
+		return response
+	}
+
+	response.Reachable = true
+	response.LatencyMs = pingResult.LatencyMs
+	s.logger.Debug("ping OK", "ip", ip, "latency_ms", pingResult.LatencyMs)
+
+	// Step 2: Run all probers in parallel
+	type probeResult struct {
+		name string
+		data any
+		err  error
+	}
+
+	results := make(chan probeResult, len(s.probers))
+	var wg sync.WaitGroup
+
+	for _, p := range s.probers {
+		wg.Add(1)
+		go func(prober Prober) {
+			defer wg.Done()
+			data, err := prober.Probe(ctx, ip)
+			results <- probeResult{
+				name: prober.Name(),
+				data: data,
+				err:  err,
+			}
+		}(p)
+	}
+
+	// Close results channel when all probers finish
+	go func() {
+		wg.Wait()
+		close(results)
+	}()
+
+	// Collect results
+	for r := range results {
+		if r.err != nil {
+			s.logger.Debug("prober failed", "prober", r.name, "error", r.err.Error())
+			continue
+		}
+		if r.data == nil {
+			continue
+		}
+
+		switch r.name {
+		case "dns":
+			if v, ok := r.data.(*models.DNSProbeResult); ok {
+				response.Probes.DNS = v
+			}
+		case "arp":
+			if v, ok := r.data.(*models.ARPProbeResult); ok {
+				response.Probes.ARP = v
+			}
+		case "mdns":
+			if v, ok := r.data.(*models.MDNSProbeResult); ok {
+				response.Probes.MDNS = v
+			}
+		}
+	}
+
+	// Step 3: Determine type based on probe results
+	response.Type = s.determineType(response)
+
+	s.logger.Info("probe completed",
+		"ip", ip,
+		"reachable", response.Reachable,
+		"type", response.Type,
+		"latency_ms", response.LatencyMs,
+	)
+
+	return response
+}
+
+// determineType decides the device type based on collected probe results.
+func (s *ProbeService) determineType(response *models.ProbeResponse) string {
+	if !response.Reachable {
+		return ProbeTypeUnreachable
+	}
+
+	// HomeKit camera that is not yet paired
+	if response.Probes.MDNS != nil && !response.Probes.MDNS.Paired {
+		category := response.Probes.MDNS.Category
+		if category == "camera" || category == "doorbell" {
+			return ProbeTypeHomeKit
+		}
+	}
+
+	return ProbeTypeStandard
+}