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/oui.go

@@ -0,0 +1,76 @@
+package discovery
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"strings"
+	"sync"
+)
+
+// OUIDatabase provides MAC address prefix to vendor name lookup.
+// Data is loaded from a JSON file containing camera/surveillance vendor OUI prefixes.
+type OUIDatabase struct {
+	data map[string]string // "C0:56:E3" -> "Hikvision"
+	mu   sync.RWMutex
+}
+
+// NewOUIDatabase creates an empty OUI database.
+func NewOUIDatabase() *OUIDatabase {
+	return &OUIDatabase{
+		data: make(map[string]string),
+	}
+}
+
+// LoadFromFile loads OUI data from a JSON file.
+// Expected format: {"C0:56:E3": "Hikvision", "54:EF:44": "Lumi/Aqara", ...}
+func (db *OUIDatabase) LoadFromFile(path string) error {
+	file, err := os.Open(path)
+	if err != nil {
+		return fmt.Errorf("failed to open OUI database: %w", err)
+	}
+	defer file.Close()
+
+	var data map[string]string
+	if err := json.NewDecoder(file).Decode(&data); err != nil {
+		return fmt.Errorf("failed to decode OUI database: %w", err)
+	}
+
+	// Normalize all keys to uppercase
+	normalized := make(map[string]string, len(data))
+	for k, v := range data {
+		normalized[strings.ToUpper(k)] = v
+	}
+
+	db.mu.Lock()
+	db.data = normalized
+	db.mu.Unlock()
+
+	return nil
+}
+
+// LookupVendor returns the vendor name for a given MAC address.
+// MAC can be in any format: "C0:56:E3:AA:BB:CC", "c0:56:e3:aa:bb:cc", "C0-56-E3-AA-BB-CC".
+// Returns empty string if not found.
+func (db *OUIDatabase) LookupVendor(mac string) string {
+	if len(mac) < 8 {
+		return ""
+	}
+
+	// Normalize: uppercase and replace dashes with colons
+	prefix := strings.ToUpper(mac[:8])
+	prefix = strings.ReplaceAll(prefix, "-", ":")
+
+	db.mu.RLock()
+	vendor := db.data[prefix]
+	db.mu.RUnlock()
+
+	return vendor
+}
+
+// Size returns the number of entries in the database.
+func (db *OUIDatabase) Size() int {
+	db.mu.RLock()
+	defer db.mu.RUnlock()
+	return len(db.data)
+}