Add analysis preview to case list

Introduce a `preview_lines` setting in `users.toml` to control the
number of visible lines for the analysis preview in the case list. This
feature extracts the first paragraph of the `document.md` file, strips
markdown formatting, and displays it, capped by the configured
`preview_lines`. The actual line clamping is handled client-side via CSS
`line-clamp`.

server/users.toml.example

@@ -8,6 +8,11 @@ slug = "dr_mueller"
 api_key = "change-me-to-a-secure-key"
 web_password = "$2b$12$..."
 role = "doctor"
+  # Optional: how many visual lines of the LLM analysis preview the case
+  # list renders under each row. The preview itself is always the first
+  # paragraph of document.md; this value only caps the visible lines
+  # before truncation with "…". Defaults to 2 if omitted.
+  preview_lines = 2
   # Optional per-user retention. Both fields default to 0 (feature
   # disabled). auto_close_days = 7 + auto_delete_days = 30 means cases
   # without new recordings auto-close after 7 days and are irreversibly