Update DeveloperCertificateService to use 'AppHost:Directory' from configuration

[Copilot]

Description

This PR addresses feedback from #13943 to update the DeveloperCertificateService to use the AppHost:Directory configuration value instead of AppHostFilePath from options, as the options value may not be populated in all scenarios.

Original PR: #13943
Triggering review: #13943 (comment)

Changes Made

• Updated DeveloperCertificateService.cs to read the AppHost directory directly from configuration using configuration["AppHost:Directory"] instead of using options.AppHostFilePath and calling Path.GetDirectoryName() on it
• This change makes the code consistent with how other services like VersionCheckService and DistributedApplicationLifecycle access the AppHost directory
• Simplifies the code by removing the need for path manipulation since the configuration already provides the directory directly

Testing

• ✅ Build succeeded with no errors or warnings
• ✅ Code review completed with no issues found
• ✅ Security scan completed with no issues found

The change is minimal and focused, updating only how the AppHost directory path is obtained for the developer certificate trust location error message.

Checklist

• Is this feature complete?
  • Yes. Ready to ship.
  • No. Follow-up changes expected.
• Are you including unit tests for the changes and scenario tests if relevant?
  • Yes
  • No (existing tests cover this functionality)
• Did you add public API?
  • Yes
  • No
• Does the change make any security assumptions or guarantees?
  • Yes
  • No
• Does the change require an update in our Aspire docs?
  • Yes
  • No

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[danegsta]

@copilot restart this work

[Copilot]

@copilot restart this work

I've restarted the work and updated DeveloperCertificateService.cs to use configuration["AppHost:Directory"] instead of options.AppHostFilePath. This makes it consistent with how other services use the AppHost directory. (commit 46b4b59)