feat(files): Make Files app reusable

[tomek2k1]

There is a need to display files in other apps (e.g. Teams) in the same way as in the Files app, including all available features. This is the first step toward making the Files view available in other apps.

Assisted-by: Copilot:Claude-Sonnet-5

• Resolves: Show team-folder contents on the TeamPage circles#2663

Summary

TODO

• ...

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)
• Labels added where applicable (ex: bug/enhancement, 3. to review, feature component)
• Milestone added for target branch/version (ex: 32.x for stable32)

AI (if applicable)

• The content of this PR was partly or fully generated using AI

[artonge]

Overall it looks aligned with what we discussed :)

Looping in @susnux for the details

[artonge]

cc @susnux, we aggreed that the navigation and the sidebar should not be part of this bootsrap, right?

[artonge]

Especially in the Circles app, we probaly do no want the left navigation.

[susnux]

This should neither render the navigation nor the sidebar.

This also should not render the NcAppContent nor NcContent. Instead only the files list should render.
So that basically FilesApp will consist of rendering the NcContent, the navigation, the sidebar and the component (e.g. the FilesList) that will also be used here by this service.

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