High CPU usage when idle, possibly DNS related

**Describe the issue**:
I'm seeing high CPU usage (4-6% on an 18 core/36 thread CPU) by "Service Host: DNS Client" associated with dask workers, even when they're not running tasks. Wireshark doesn't show any actual DNS traffic, even on loopback, but I can make the CPU usage start and stop reliably by starting or stopping the workers.

It seems to scale with the number of workers; if I start 100 workers it goes even higher.

**Minimal Complete Verifiable Example**:
```
mkdir testing
cd testing
uv init --python 3.12
uv add dask[distributed]
uv run dask scheduler
# In a separate window
uv run dask worker tcp://127.0.0.1:8786 --nworkers 36 --nthreads 1
```
Then observe CPU usage in task manager.

**Environment**:

- Dask version: 2025.11.0
- Python version: 3.12.10
- Operating System: Microsoft Windows [Version 10.0.19045.6456]
- Install method: uv