Fix seed_tailscale_peers to use CurAddr field not Endpoints

tailscale status --json uses CurAddr for the active direct endpoint,
not Endpoints (which is always null/absent). Without this fix the
Tailscale exclusion set was always empty.

net_alerter/net_alerter.py

@@ -856,8 +856,10 @@ def seed_tailscale_peers() -> None:
         status = json.loads(result.stdout)
         peer_ips = set()
         for peer in status.get('Peer', {}).values():
-            for ep in peer.get('Endpoints', []):
-                ip = ep.split(':')[0]
+            # CurAddr is the active direct endpoint (e.g. "10.0.0.0:41641")
+            cur = peer.get('CurAddr', '')
+            if cur:
+                ip = cur.rsplit(':', 1)[0]
                 if ip:
                     peer_ips.add(ip)
         if not peer_ips: