feat(teams): add ITeamFileResourceProvider for cross-provider file lookups

[pringelmann]

• Resolves: Implement a team resource provider  groupfolders#2845

Summary

The teams lookup asks a single provider, picked by the providerId in the route. For a file that is always files, which circles owns and answers from oc_share. A team folder is mounted rather than shared, so there is no share row, the answer comes back empty, and the sidebar card hides itself.

This adds ITeamFileResolver, one interface with one method. When the lookup was addressed by file id, TeamManager also asks every provider implementing it and merges the result. groupfolders does the answering in nextcloud/groupfolders#5035.

Tested on a team space, a folder shared with a team, files two levels deep, and a file belonging to no team. A Deck board on the same team lands in the same card:

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 (tests)