feat: Add API endpoint for listing oneliners

This commit introduces a new API endpoint `/api/oneliners` that allows
authenticated users to retrieve a list of their recent oneliners.

The endpoint supports conditional GET requests using the `ETag` header
for efficient caching. It also allows specifying a time window for the
oneliners via the `hours` query parameter, with sensible defaults and
clamping.

The implementation includes:
- A new route handler `handle_oneliners`.
- A new type `OnelinerWatermark` for tracking user-specific timestamps.
- Logic for scanning user data directories, filtering by time, and
  handling deleted cases.
- Test cases to cover various scenarios, including caching, time
  windowing, and edge cases.

server/src/main.rs

@@ -12,7 +12,7 @@ use doctate_server::analyze;
 use doctate_server::config::Config;
 use doctate_server::gazetteer::{Gazetteer, SpellbookDict};
 use doctate_server::transcribe;
-use doctate_server::AppState;
+use doctate_server::{AppState, OnelinerWatermark};
 
 #[tokio::main]
 async fn main() {
@@ -110,6 +110,13 @@ async fn main() {
         }
     });
 
+    // Oneliner watermark: per-user "last successful oneliner write (UTC)".
+    // Feeds the ETag on `/api/oneliners`. Shared across the transcribe
+    // worker (writer) and the oneliners route handler (reader).
+    let oneliner_watermark: OnelinerWatermark = Arc::new(tokio::sync::RwLock::new(
+        std::collections::HashMap::new(),
+    ));
+
     // Transcription pipeline: channel + worker + recovery scan.
     let (transcribe_tx, transcribe_rx) = transcribe::channel();
     let transcribe_busy: doctate_server::WorkerBusy =
@@ -120,6 +127,7 @@ async fn main() {
         http_client.clone(),
         transcribe_busy.clone(),
         vocab.clone(),
+        oneliner_watermark.clone(),
     ));
     {
         let tx = transcribe_tx.clone();
@@ -127,11 +135,15 @@ async fn main() {
         let client = http_client.clone();
         let cfg = config.clone();
         let vocab = vocab.clone();
+        let watermark = oneliner_watermark.clone();
         tokio::spawn(async move {
             transcribe::recovery::scan_and_enqueue(&data_path, &tx).await;
             // Then catch up oneliners for cases that crashed between
             // transcript-write and oneliner-write in a previous run.
-            transcribe::recovery::regenerate_missing_oneliners(&data_path, &client, &cfg, &vocab).await;
+            transcribe::recovery::regenerate_missing_oneliners(
+                &data_path, &client, &cfg, &vocab, &watermark,
+            )
+            .await;
         });
     }
 
@@ -161,6 +173,7 @@ async fn main() {
         session_store: doctate_server::web_session::new_store(),
         analyze_busy: doctate_server::AnalyzeBusy(analyze_busy),
         transcribe_busy: doctate_server::TranscribeBusy(transcribe_busy),
+        oneliner_watermark,
     };
 
     let addr = format!("0.0.0.0:{}", config.server_port);