Opening documents in external app (OnlyOffice/WOPI) returns client-side 404 - race condition with /app/list on full page navigation

### Describe the bug

[bug-report-external-app-404.md](https://github.com/user-attachments/files/29742108/bug-report-external-app-404.md)

### Steps to reproduce

```textarea
1.el issue que es reproducible en una instalación bare-metal real con datos reales
2.
3.
...
```

### Expected behavior

Open editor normally

### Actual behavior

error 404

### Setup

```markdown
- Web version:
- oCIS version:
- browser:

OCIS_XXX=somevalue
OCIS_YYY=somevalue
PROXY_XXX=somevalue
```

### Additional context

_No response_

Start by reading the attached bug report and tracing the full-page navigation that reaches /app/list when opening a document in OnlyOffice/WOPI. Reproduce it on a bare-metal installation with real data, then verify that the editor opens normally without the client-side 404.

Written by the indexing model from the issue text.