Add event bus for live UI updates

Introduces a system for broadcasting real-time events to the web UI.
This enables features like automatic page reloads when case data changes
in the background, improving the user experience by keeping the UI
synchronized with the backend.

Key components:
- `events` module: Contains the `CaseEventKind` enum, `CaseEvent`
  struct, and `EventSender` type for managing the broadcast channel.
- SSE endpoint (`/web/events`): Streams events to connected browsers.
- Client-side JavaScript: Listens for events and triggers debounced page
  reloads.
- Integration points: Workers and route handlers now emit events when
  relevant state changes occur.

server/src/main.rs

@@ -11,6 +11,7 @@ use tracing_subscriber::util::SubscriberInitExt;
 use doctate_server::AppState;
 use doctate_server::analyze;
 use doctate_server::config::Config;
+use doctate_server::events;
 use doctate_server::gazetteer::{Gazetteer, SpellbookDict};
 use doctate_server::transcribe;
 
@@ -110,6 +111,11 @@ async fn main() {
         }
     });
 
+    // Live-update bus: background workers and handlers publish case
+    // events here; the SSE route at `/web/events` fans them out to
+    // subscribed browsers.
+    let events_tx = events::channel();
+
     // Transcription pipeline: channel + worker + recovery scan.
     let (transcribe_tx, transcribe_rx) = transcribe::channel();
     let transcribe_busy: doctate_server::WorkerBusy =
@@ -120,6 +126,7 @@ async fn main() {
         http_client.clone(),
         transcribe_busy.clone(),
         vocab.clone(),
+        events_tx.clone(),
     ));
     {
         let tx = transcribe_tx.clone();
@@ -127,12 +134,15 @@ async fn main() {
         let client = http_client.clone();
         let cfg = config.clone();
         let vocab = vocab.clone();
+        let events = events_tx.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, &events,
+            )
+            .await;
         });
     }
 
@@ -146,6 +156,7 @@ async fn main() {
         http_client.clone(),
         analyze_busy.clone(),
         vocab.clone(),
+        events_tx.clone(),
     ));
     {
         let tx = analyze_tx.clone();
@@ -163,6 +174,7 @@ async fn main() {
         magic_link_store: doctate_server::magic_link::new_store(),
         analyze_busy: doctate_server::AnalyzeBusy(analyze_busy),
         transcribe_busy: doctate_server::TranscribeBusy(transcribe_busy),
+        events_tx,
     };
 
     let addr = format!("0.0.0.0:{}", config.server_port);