Unknown routes silently redirect to Mine eForms; menu editor accepts links that match no route #8103

Customer report

Ryger ind på eForm-oversigt

Current behaviour

A menu entry whose link matches no route (e.g. a plugin link saved without the /plugins prefix, or a removed plugin route) silently redirects to "Mine eForms" through the catch-all route {path: '**', redirectTo: ''}. The user gets no hint that the link is wrong, and admins can save such links in the menu editor without a warning. Menu saves delete and re-insert every item, so there is no trace of who changed a link.

Fix sketch

1. Replace the silent redirect with a "Siden blev ikke fundet" page that shows the requested URL and a link to the start page.
2. Menu editor: warn when an internal link matches no registered route; offer "restore default link" for items that come from a plugin template.
3. Optional: record who saved the menu and when; make the menu save a single transaction.

Tests

• Playwright: navigate to an unknown URL → the not-found page shows the URL (no redirect).
• Menu editor: entering an internal link that matches no route shows the warning.