Fix async station refresh to rebuild list correctly

[dtseto]

Summary

• rebuild the async station refresh flow so it always constructs the full station list before publishing it
• keep quick mix stations and normal stations together while honoring the selected sort order and awaiting rating metadata
• update the station metadata helper to operate on a supplied station set and handle missing station payloads gracefully

Testing

• dotnet build (fails: dotnet not installed in container)

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https://chatgpt.com/codex/tasks/task_e_69029330190083329e5bd93d313dc7d7