Element Desktop crashes with unhandled exception when auto-update check is blocked by network/firewall

[Squirrel-CheckForUpdate.log](https://github.com/user-attachments/files/30933041/Squirrel-CheckForUpdate.log)

### Steps to reproduce

Start Element Desktop on a Windows machine connected to a corporate network that restricts outbound traffic (specifically blocking packages.element.io or Cloudflare IPs).
Wait for the background update check to trigger, or manually check for updates.
The Squirrel Updater attempts to download the RELEASES file.
The connection is refused by the proxy/firewall.

### Outcome

What did you expect?
The application should fail gracefully. If it cannot reach the update server, it should simply log a warning, perhaps show a non-intrusive UI notification ("Update check failed"), and allow me to continue using the chat application. Older versions of Element behaved exactly like this and did not crash.

What happened instead?
The application completely crashes. The Squirrel updater throws a fatal unhandled exception (System.AggregateException -> System.Net.WebException) because it cannot handle the connection refusal. Because the app crashed, I was forced to download the new installer and manually update the application to bypass the crash loop.

### Operating system

win 11

### Application version

v1.12.24

### How did you install the app?

_No response_

### Homeserver

_No response_

### Will you send logs?

Yes

Reproduce the failure on Windows by blocking access to packages.element.io or Cloudflare IPs, then inspect Squirrel-CheckForUpdate.log and the Squirrel updater entry point. Trace the failed RELEASES download and verify that the application remains usable and records a warning instead of terminating.

Written by the indexing model from the issue text.