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/api/handlers/probe.go

@@ -0,0 +1,82 @@
+package handlers
+
+import (
+	"encoding/json"
+	"net"
+	"net/http"
+
+	"github.com/eduard256/Strix/internal/camera/discovery"
+)
+
+// ProbeHandler handles device probe requests.
+// GET /api/v1/probe?ip=192.168.1.50
+type ProbeHandler struct {
+	probeService *discovery.ProbeService
+	logger       interface {
+		Debug(string, ...any)
+		Error(string, error, ...any)
+		Info(string, ...any)
+	}
+}
+
+// NewProbeHandler creates a new probe handler.
+func NewProbeHandler(
+	probeService *discovery.ProbeService,
+	logger interface {
+		Debug(string, ...any)
+		Error(string, error, ...any)
+		Info(string, ...any)
+	},
+) *ProbeHandler {
+	return &ProbeHandler{
+		probeService: probeService,
+		logger:       logger,
+	}
+}
+
+// ServeHTTP handles probe requests.
+func (h *ProbeHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	if r.Method != http.MethodGet {
+		http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
+		return
+	}
+
+	ip := r.URL.Query().Get("ip")
+	if ip == "" {
+		h.sendError(w, "Missing required parameter: ip", http.StatusBadRequest)
+		return
+	}
+
+	// Validate IP format
+	if net.ParseIP(ip) == nil {
+		h.sendError(w, "Invalid IP address: "+ip, http.StatusBadRequest)
+		return
+	}
+
+	h.logger.Info("probe requested", "ip", ip, "remote_addr", r.RemoteAddr)
+
+	// Run probe
+	result := h.probeService.Probe(r.Context(), ip)
+
+	// Send response
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(http.StatusOK)
+
+	if err := json.NewEncoder(w).Encode(result); err != nil {
+		h.logger.Error("failed to encode probe response", err)
+	}
+}
+
+// sendError sends a JSON error response.
+func (h *ProbeHandler) sendError(w http.ResponseWriter, message string, statusCode int) {
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(statusCode)
+
+	response := map[string]interface{}{
+		"error":   true,
+		"message": message,
+		"code":    statusCode,
+	}
+
+	_ = json.NewEncoder(w).Encode(response)
+}