GHSA-9wgh-m22w-9xj8

### Summary The public shared-view relation endpoints accepted a caller-supplied column ID without verifying that the column was visible in the shared view, so anyone holding a share UUID could read links from any LTAR column on the view's table — including columns the view owner had hidden.

### Details `publicMmList`, `publicHmList`, and `relDataList` already ensured that the requested column belonged to the view's model, but did not check the view-column entry's `show` flag. All three handlers now also fetch the shared view's column entries and reject the request unless the matching entry has `show=true`. The four public relation routes covered by the fix are:

- `GET /api/v2/public/shared-view/:uuid/rows/:rowId/mm/:columnId` (many-to-many) - `GET /api/v2/public/shared-view/:uuid/rows/:rowId/hm/:columnId` (has-many) - `GET /api/v2/public/shared-view/:uuid/rows/:rowId/{ln,om}/:columnId` (links / one-to-many — both share the many-to-many handler) - `GET /api/v2/public/shared-view/:uuid/nested/:columnId` (form/gallery picker)

### Impact Anyone holding a share UUID could enumerate the full set of linked records for any hidden LTAR column on the view's table by calling the relation endpoint directly, even when the same column was correctly omitted from the public `/rows` response.

### Credit This issue was reported by [@leduckhuong](https://github.com/leduckhuong).