TREK: Cross-trip reservation title disclosure via file links

TREK is a collaborative travel planner. Prior to 3.1.3, TREK file upload, update, and link actions accept attacker-controlled reservation_id, place_id, and assignment_id values without using findForeignLinkTarget() to verify that the referenced object belongs to the file's trip. An authenticated user with file-edit permission on any accessible trip can submit a foreign reservation identifier through POST /api/trips/:tripId/files/:id/link, POST /api/trips/:tripId/files, or PUT /api/trips/:tripId/files/:id. Subsequent reads through FILE_SELECT or getFileLinks() join the foreign reservation and return reservation_title, disclosing reservation existence and titles across private trip boundaries. This issue is fixed in version 3.1.3.