As a Proton Drive web user, I want a single, permanent “universal” link per file that is scoped to “anyone with existing access,” so that:
- users who already have access can open the file directly via the link,
- users who do not have access are shown a clear option to request access from the owner,
- I can use the same link myself as a fast internal shortcut (for example from a Notes or Todo app).

Acceptance criteria:
1. Each file page provides a “Copy universal link (anyone with existing access)” action.
2. The link is permanent and does not change when the file is renamed or metadata is updated.
3. Visiting the link with an account that has access opens the file immediately without extra prompts.
4. Visiting the link without access shows a clear “Request access” flow to contact the owner and optionally include a message.
5. The link reliably functions as an internal shortcut from external apps (e.g., notes, todo apps).
6. File permissions and protections (view/edit roles, expirations, passwords) remain enforced and are not bypassed by the link.
7. Use of the universal link and subsequent access requests/grants are recorded in audit logs.