Migrate off the OCA.Viewer global before Nextcloud 36

Tables opens images from a cell in the viewer:

• src/shared/components/ncTable/NcTable.vue:416: OCA.Viewer.open({ path: filePath, list: [{ filename: filePath }] })

Both arguments change shape: the viewer takes @nextcloud/files nodes, so the hand-built
{ filename } list object is not accepted. If all you have is the path, openFolder(folder, file)
will fetch, or build the node yourself.

OCA.Viewer is gone in Viewer 7.0.0. The viewer ships as the
@nextcloud/viewer library rather than a
bundled app, and nextcloud/server#63954 removes the viewer app from Nextcloud 36 altogether.

Roughly what it looks like:

import { canView, getViewer } from '@nextcloud/viewer'

// OCA.Viewer.open({ path }) / ({ fileInfo, list })
getViewer().open(nodes, file)          // @nextcloud/files nodes
getViewer().openFolder(folder, file)   // when a path is all you have, let it fetch

// OCA.Viewer.mimetypes.includes(mime) / availableHandlers
canView(node)

The part that is not a rename is that the viewer takes @nextcloud/files nodes now, not
fileinfo objects or path strings. Importing the package is also all it takes to get the viewer
onto the page: no LoadViewer event to dispatch, and nothing to check about whether the app is
enabled.

[!IMPORTANT]
There is no compatibility shim, which was a deliberate call, so this is a real port rather
than a rename. Nothing breaks until the server PR lands; after that these calls throw on
Nextcloud 36.

[!TIP]
The developer manual covers the migration under
Critical changes
(being added in nextcloud/documentation#15597), and the
README
has the full before/after table. Happy to help with the port, just ping me.

_{👾 This issue was written with the help of Claude Code.}

Start at src/shared/components/ncTable/NcTable.vue:416 and review the @nextcloud/viewer README migration guide linked in the issue. Trace how the table obtains its file path, then port the viewer call to the node-based API or openFolder path described there. Done means the table opens images without OCA.Viewer, LoadViewer, or viewer-app checks and remains compatible with Nextcloud 36.