feat: detect virtual machines from MAC OUI and show badge on pending devices

Backend:
- Add MAC OUI lookup table (QEMU 52:54:00, Proxmox bc:24:11, VMware, VBox, Hyper-V)
- suggest_node_type() now accepts mac param and uses OUI as a low-priority hint

Frontend:
- Detect VM type from MAC prefix on pending device cards
- Show colored badge (QEMU / PVE / VMware / VBox / Hyper-V) in orange with tooltip

backend/app/services/scanner.py

@@ -113,7 +113,7 @@ async def run_scan(ranges: list[str], db: AsyncSession, run_id: str) -> None:
 
             for host in hosts:
                 services = fingerprint_ports(host["open_ports"])
-                suggested_type = suggest_node_type(host["open_ports"])
+                suggested_type = suggest_node_type(host["open_ports"], host.get("mac"))
 
                 # Update existing pending device or create a new one
                 existing_result = await db.execute(