Fix: shared gallery person management (allows operations with correct WebDAV permissions)

[jacksbox-cassandra]

Fix shared gallery person management permissions

Problem

Users cannot manage face clusters (rename, move, merge faces) for photos uploaded by other users in shared galleries, even when they have full permissions to the shared folder.

Error message: "Only user '{user}' can update this person"

This prevents collaborative face organization in shared family or group galleries.

Root Cause

The frontend components had strict ownership checks (this.user !== utils.uid) that blocked all face management operations on clusters belonging to other users, regardless of shared folder permissions.

Solution

• Added canManagePersonCluster(personUserId) helper function that checks WebDAV permissions
• Updated all face management modals to use permission-based access control instead of strict ownership
• Preserves security by only allowing operations when users have write permissions to the relevant files

Changes Made

1. New Permission Helper (src/services/utils/helpers.ts):

   • canManagePersonCluster() function using PROPFIND WebDAV requests
   • Checks for write permissions ('W' flag) in oc:permissions
   • Falls back to current user only if permission check fails

2. Updated Components:

   • FaceEditModal.vue - Person renaming
   • FaceMoveModal.vue - Moving faces between persons
   • FaceMergeModal.vue - Merging face clusters
   • SelectionManager.vue - Removing faces from persons

Testing

• ✅ Project builds successfully
• ✅ TypeScript compilation passes
• ✅ Backward compatibility maintained
• ✅ No breaking API changes

Security Considerations

• Permission checks are done on each operation
• Falls back to restrictive behavior if permissions cannot be determined
• Uses existing Nextcloud WebDAV permission system
• No new security vulnerabilities introduced

Fixes

Closes #290