Network Failure when Creating new app

### Environment information

```plain text
System:
OS: Windows 11 10.0.26100
CPU: (16) x64 13th Gen Intel(R) Core(TM) i5-13500H
Memory: 4.92 GB / 15.70 GB
Binaries:
Node: 20.18.3 - C:\Program Files\nodejs\node.EXE
Yarn: undefined - undefined
npm: 11.1.0 - C:\Program Files\nodejs\npm.CMD
pnpm: undefined - undefined
NPM Packages:
@aws-amplify/auth-construct: 1.6.0
@aws-amplify/backend: 1.14.1
@aws-amplify/backend-ai: Not Found
@aws-amplify/backend-auth: 1.5.0
@aws-amplify/backend-cli: 1.4.11
@aws-amplify/backend-data: 1.4.0
@aws-amplify/backend-deployer: 1.1.18
@aws-amplify/backend-function: 1.12.2
@aws-amplify/backend-output-schemas: 1.4.0
@aws-amplify/backend-output-storage: 1.1.4
@aws-amplify/backend-secret: 1.1.6
@aws-amplify/backend-storage: 1.2.4
@aws-amplify/cli-core: 1.3.0
@aws-amplify/client-config: 1.5.7
@aws-amplify/data-construct: 1.15.0
@aws-amplify/data-schema: 1.18.0
@aws-amplify/deployed-backend-client: 1.5.1
@aws-amplify/form-generator: 1.0.4
@aws-amplify/model-generator: 1.0.12
@aws-amplify/platform-core: 1.6.3
@aws-amplify/plugin-types: 1.8.0
@aws-amplify/sandbox: 1.2.11
@aws-amplify/schema-generator: 1.2.7
aws-amplify: 6.13.2
aws-cdk: 2.1002.0
aws-cdk-lib: 2.181.1
typescript: 5.8.2
No AWS environment variables
No CDK environment variables
```

### Describe the bug

When i try to create a new app with Gthub Provider, i get "Network Failure" and i can't select any repository. I'm having this issue for a week. I didn't used AWS or Amplify before.
- I tired to Uninstall Amplify app from my Github profile, then tired to create Amplify app again.
- I can reproduce with private browsing. I use Firefox if matters.
- I disabled browser tracking protection.

These are XHR requests i see in dev tools when i got "Network Failure".

There is setting for "AWS Amplify (eu-central-1)" app in my Github

### Reproduction steps

1. Create a new app, select Github provider then next.

2. Github popup shows for a second then closes.

3. Get the "Network Failure". There is nothing in the repository list. Clicking "Update Github Permissions" has no effect.

Reproduce the failure using the listed steps, then inspect the XHR requests and GitHub authorization popup in Firefox, including private browsing. Done means the GitHub repository list loads when creating a new Amplify app, or the issue is narrowed to a documented external service or permission failure.

Written by the indexing model from the issue text.