feat(analysis): live SSE event stream for the admin dashboard

Broadcasts analysis progress so the dashboard updates live:

- analysis::events: AnalysisEvents broadcaster + AnalysisEvent
  (Enqueued / Started / Completed / Failed), carrying the
  manga/chapter/page breadcrumb.
- The worker daemon resolves each page's breadcrumb (repo::page::locate)
  and publishes Started before dispatch and Completed/Failed after.
- The admin reenqueue publishes Enqueued (scoped by manga/chapter).
- GET /v1/admin/analysis/status/stream — SSE (RequireAdmin) forwarding
  each event as a named `analysis` frame; broadcast lag emits a `lagged`
  frame. AppState carries the always-present events bus.

Tests: worker publishes started+completed (with breadcrumb) and failed;
SSE route is admin-gated (403 non-admin) and returns text/event-stream.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

backend/src/analysis/daemon.rs

@@ -22,6 +22,7 @@ use tokio::task::JoinSet;
 use tokio_util::sync::CancellationToken;
 use uuid::Uuid;
 
+use crate::analysis::events::{AnalysisEvent, AnalysisEvents};
 use crate::analysis::vision::VisionClient;
 use crate::crawler::jobs::{self, JobPayload, Lease, KIND_ANALYZE_PAGE};
 use crate::repo;
@@ -43,6 +44,8 @@ pub struct AnalysisDaemonConfig {
     pub dispatcher: Arc<dyn AnalyzeDispatcher>,
     pub workers: usize,
     pub job_timeout: Duration,
+    /// Live-event sink (Started/Completed/Failed) for admin SSE.
+    pub events: Arc<AnalysisEvents>,
 }
 
 pub struct AnalysisDaemonHandle {
@@ -71,6 +74,7 @@ pub fn spawn(
             cancel: cancel.clone(),
             dispatcher: Arc::clone(&cfg.dispatcher),
             job_timeout: cfg.job_timeout,
+            events: Arc::clone(&cfg.events),
             id,
         };
         join.spawn(async move { ctx.run().await });
@@ -83,6 +87,7 @@ struct WorkerContext {
     cancel: CancellationToken,
     dispatcher: Arc<dyn AnalyzeDispatcher>,
     job_timeout: Duration,
+    events: Arc<AnalysisEvents>,
     id: usize,
 }
 
@@ -143,6 +148,20 @@ impl WorkerContext {
             }
         }
 
+        // Resolve the page breadcrumb once so live events carry the
+        // manga/chapter/number the dashboard keys on. A missing breadcrumb
+        // (page deleted) just suppresses events — the dispatch still runs
+        // and acks normally.
+        let breadcrumb = repo::page::locate(&self.pool, page_id).await.ok().flatten();
+        if let Some((manga_id, chapter_id, page_number)) = breadcrumb {
+            self.events.publish(AnalysisEvent::Started {
+                page_id,
+                manga_id,
+                chapter_id,
+                page_number,
+            });
+        }
+
         // Heartbeat the lease while the vision call runs.
         let heartbeat = {
             let hb_pool = self.pool.clone();
@@ -171,6 +190,15 @@ impl WorkerContext {
             Ok(Ok(Ok(()))) => Ok(()),
         };
 
+        if let Some((manga_id, chapter_id, page_number)) = breadcrumb {
+            let event = if result.is_ok() {
+                AnalysisEvent::Completed { page_id, manga_id, chapter_id, page_number }
+            } else {
+                AnalysisEvent::Failed { page_id, manga_id, chapter_id, page_number }
+            };
+            self.events.publish(event);
+        }
+
         match result {
             Ok(()) => {
                 let _ = jobs::ack_done(&self.pool, lease.id).await;