refactor(db-repository): extract push folders query logic to PushFoldersQueryRepository

[rafaeltonholo]

Contribution Summary

Linked Issue/Ticket: Part of #11470

Description

• Add PushFoldersQueryRepository interface with observeAllByAccountId and getAllByAccountId methods
• Add DefaultPushFoldersQueryRepository implementation
• Remove getPushFoldersFlow and getPushFolders from FolderRepository
• Update AccountPushController to use new repository and handle Outcome
• Add comprehensive tests for DefaultPushFoldersQueryRepository

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• This contribution is in Kotlin where possible
• This contribution does not use merge commits
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• This contribution includes tests for any new functionality, and maintains tests for any updated functionality.
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• This PR has a descriptive title and body that accurately outlines all changes made, and contains a reference to any issues that it fixes (e.g. Closes #XXX or Fixes #XXX).

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