Rewrite Strix from scratch as single binary

Complete architecture rewrite following go2rtc patterns:
- pkg/ for pure logic (camdb, tester, probe, generate)
- internal/ for application glue with Init() modules
- Single HTTP server on :4567 with all endpoints
- zerolog with password masking and memory ring buffer
- Environment-based config only (no YAML files)

API endpoints: /api/search, /api/streams, /api/test,
/api/probe, /api/generate, /api/health, /api/log

Dependencies: go2rtc v1.9.14, go-sqlite3, miekg/dns, zerolog

pkg/probe/arp.go

@@ -0,0 +1,35 @@
+package probe
+
+import (
+	"bufio"
+	"os"
+	"strings"
+)
+
+// LookupARP reads /proc/net/arp to find MAC address for ip. Linux only.
+func LookupARP(ip string) string {
+	file, err := os.Open("/proc/net/arp")
+	if err != nil {
+		return ""
+	}
+	defer file.Close()
+
+	scanner := bufio.NewScanner(file)
+	scanner.Scan() // skip header
+
+	for scanner.Scan() {
+		fields := strings.Fields(scanner.Text())
+		if len(fields) < 4 {
+			continue
+		}
+		if fields[0] == ip {
+			mac := fields[3]
+			if mac == "00:00:00:00:00:00" {
+				return ""
+			}
+			return strings.ToUpper(mac)
+		}
+	}
+
+	return ""
+}