fix(files_sharing): normalize share target on parent folder rename

[silverkszlo]

Summary

When a recipient moved an incoming share into one of their own folders and later renamed that folder, Updater::renameChildren passed the mount point to SharedMount::moveMount. Mount points always end in a slash, and stripUserFilesPath did not normalize its result, so the slash was stored in share.file_target. PROPFIND on such a share then returns 500.

Normalize the stripped path so no caller can write a trailing slash, and repair rows that are already affected.

To reproduce

• As owner: create test.odt (or a folder) in Files and share it with recipient
• As recipient: create your own folder at home root, e.g. box
• As recipient: move the received test.odt into box
• As recipient: rename box, e.g. "box_renamed"
• Then check occ share:list --recipient=[recipient]
  → The name of the share has a trailing slash in target-path: /box_renamed/test.odt/

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