feat: improve service detection — expanded signatures, port hints, better nmap args

- Expand service_signatures.json from 35 → ~120 entries covering *arr apps,
  smart-home (HA, MQTT, ESPHome), cameras (RTSP, Dahua, Tapo, Reolink),
  network gear (MikroTik, UniFi, Pi-hole), auth (Authelia, Authentik, Vault),
  monitoring (Grafana, InfluxDB, Loki, Uptime Kuma), containers (Portainer),
  and many more home lab services
- Expand nmap port range to cover home lab ports (8989, 7878, 8123, 554, 1883, etc.)
  and increase --host-timeout from 30s to 120s for reliable -sV detection
- Add _PORT_TYPE_HINTS fallback in suggest_node_type for ports without signatures
  (cameras→iot, MQTT→iot, Proxmox→proxmox, MikroTik→router, etc.)
- Show actual port/protocol (e.g. TCP/9999) instead of "unknown_service" so
  all open ports are visible even when not matched
- Update tests to reflect new unknown-port label format

backend/tests/test_fingerprint.py

@@ -71,7 +71,7 @@ def test_fingerprint_ports_known_ports():
 def test_fingerprint_ports_unknown_port():
     results = fingerprint_ports([{"port": 9999, "protocol": "tcp"}])
     assert len(results) == 1
-    assert results[0]["service_name"] == "unknown_service"
+    assert results[0]["service_name"] == "TCP/9999"
     assert results[0]["icon"] is None
     assert results[0]["category"] is None
 
@@ -79,7 +79,7 @@ def test_fingerprint_ports_unknown_port():
 def test_fingerprint_ports_mixed():
     results = fingerprint_ports([{"port": 22, "protocol": "tcp"}, {"port": 9999, "protocol": "tcp"}])
     assert results[0]["service_name"] == "SSH"
-    assert results[1]["service_name"] == "unknown_service"
+    assert results[1]["service_name"] == "TCP/9999"
 
 
 def test_fingerprint_ports_empty():