Simplenote fails to sync through proxy using custom SSL certificate

At work we must use a system-wide proxy for security scanning. This proxy is a MITM, supplying its own certificate.

With the proxy enabled other apps work OK, and the Simplenote web app works, but the Simplenote Linux app cannot sync. Based on the `cert_issuer_source_aia.cc` in the stack trace (see below) it looks like the system CAs are not being used.

If I disable the proxy then Simplenote works as expected.

The proxy is configured through Ubuntu's Settings->Network->Proxy UI.

### Expected
Notes sync

### Observed
Notes permanently have the syncing spinner displayed and don't sync to the server.

```
$ simplenote --trace-warnings
Checking for beta autoupdate feature for deb/rpm distributions
Found package-type: deb
Error: unrecognized flag --no-expose-wasm
Try --help for options
[654415:0902/111414.870213:ERROR:cert_issuer_source_aia.cc(136)] AiaRequest::OnFetchCompleted got error -301
[654415:0902/111416.678551:ERROR:cert_issuer_source_aia.cc(136)] AiaRequest::OnFetchCompleted got error -301
(node:654415) UnhandledPromiseRejectionWarning: Error [ERR_UNHANDLED_ERROR]: Unhandled error. (undefined)
at ManualUpdater.emit (node:events:507:17)
at ManualUpdater.ping (/opt/Simplenote/resources/app.asar/desktop/updater/manual-updater/index.js:82:12)
at emitUnhandledRejectionWarning (node:internal/process/promises:298:15)
at warnWithErrorCodeUnhandledRejectionsMode (node:internal/process/promises:406:5)
at processPromiseRejections (node:internal/process/promises:470:17)
at process.processTicksAndRejections (node:internal/process/task_queues:96:32)
(node:654415) Error [ERR_UNHANDLED_ERROR]: Unhandled error. (undefined)
at ManualUpdater.emit (node:events:507:17)
at ManualUpdater.ping (/opt/Simplenote/resources/app.asar/desktop/updater/manual-updater/index.js:82:12)
```

Also in journalctl I see lines like the following every few minutes

```
...
Sep 02 10:48:35 FWTP5313 simplenote.desktop[289829]: [289829:0902/104835.677932:ERROR:cert_issuer_source_aia.cc(136)] AiaRequest::OnFetchCompleted got error -301
Sep 02 10:48:35 FWTP5313 simplenote.desktop[289889]: [289889:0902/104835.678327:ERROR:ssl_client_socket_impl.cc(876)] handshake failed; returned -1, SSL error code 1, net_error -202
...
```
### Where did you see the bug

- System Make: HP
- System Model: Zbook
- OS: Ubuntu
- OS version: 24.04
- Browser (if applicable): NA (Linux app)
- Browser version (if applicable): NA
- Simplenote app version: 2.23.2

Reproduce the sync failure with the Ubuntu system proxy and custom certificate enabled, then inspect the project for proxy and certificate-handling entry points. Use the cert_issuer_source_aia.cc and ssl_client_socket_impl.cc messages, along with the installed manual-updater/index.js path, to distinguish sync failure from updater errors. Done means notes sync normally through the proxy without the recurring TLS failures.

Written by the indexing model from the issue text.