Add oneliner to case view

Introduce an `oneliner` field to the `CaseView` struct and update the
`scan_cases` function to read it from `oneliner.txt`. The `cases.html`
template is updated to display the oneliner if present. A new
integration test is added to verify the functionality.

server/tests/web_test.rs

@@ -98,6 +98,7 @@ async fn web_index_shows_cases() {
         "Herzkatheter ohne Befund.",
     )
     .unwrap();
+    std::fs::write(done_case.join("oneliner.txt"), "Herzkatheter unauffällig").unwrap();
 
     let app = doctate_server::create_router(config);
     let response = app
@@ -122,6 +123,13 @@ async fn web_index_shows_cases() {
     assert!(body.contains("Transcription pending"));
     // case2 has a transcript → rendered
     assert!(body.contains("Herzkatheter ohne Befund."));
+    // case2 has an oneliner → rendered exactly once (case1 has none)
+    assert!(body.contains("Herzkatheter unauffällig"));
+    assert_eq!(
+        body.matches("class=\"oneliner\"").count(),
+        1,
+        "expected exactly one oneliner div"
+    );
 
     let _ = std::fs::remove_dir_all(&data_path);
 }