[feat](aurora-portal): Object Operations — Write

[KirylSAP]

Delete, create folders, copy, move, and edit metadata.

BFF

• Implement objects.delete (DeleteObject)
• Implement objects.createFolder (PutObject zero-byte + /)
• Implement objects.copy (CopyObject)
• Implement objects.move (CopyObject + DeleteObject)
• Implement objects.updateMetadata (CopyObject to self, REPLACE)

UI

• Add delete action with confirmation
• Create "New Folder" dialog
• Add copy/move actions with destination picker
• Create metadata editor (x-amz-meta-*)