Proposed change

When creating a new telegram bot config entry, the CONF_PROXY_URL config value is not initialized because it is nested in advanced_settings of the config flow.
Consequently, the proxy is not configured and the API validation fails with connection error.

This is a bug fix to load the value properly from the advance settings of the user input.
This should be part of the 2025.7.0 milestone.

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New integration (thank you!)
• New feature (which adds functionality to an existing integration)
• Deprecation (breaking change to happen in the future)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Additional information

• This PR fixes or closes issue: fixes The telegram bot timeout when using Cloudflare worker proxy api #147650
• This PR is related to issue:
• Link to documentation pull request:
• Link to developer documentation pull request:
• Link to frontend pull request:

Checklist

• The code change is tested and works locally.
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