perf: cache translated chapter responses for 1 hour

Translation content is immutable once generated — add Cache-Control: public,
max-age=3600, stale-while-revalidate=86400 to handleTranslationRead so the
browser and any CDN reuse the response without hitting MinIO on repeat views.
Forward the header through the SvelteKit /api/translation/[slug]/[n] proxy
which previously stripped it by constructing a bare Content-Type-only Response.

backend/internal/backend/handlers.go

@@ -1279,6 +1279,10 @@ func (s *Server) handleTranslationRead(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	// Translated chapter content is immutable once generated — cache aggressively.
+	// The browser and any intermediary (CDN, SvelteKit fetch cache) can reuse this
+	// response for 1 hour without hitting MinIO again.
+	w.Header().Set("Cache-Control", "public, max-age=3600, stale-while-revalidate=86400")
 	writeJSON(w, 0, map[string]string{"html": buf.String(), "lang": lang})
 }
 

backend/internal/backend/handlers_textgen.go

@@ -313,6 +313,8 @@ func (s *Server) handleAdminTextGenChapterNames(w http.ResponseWriter, r *http.R
 	}
 
 	// Mark job as done in PB, persisting results so the Review button works.
+	// Use context.Background() — r.Context() may be cancelled if the SSE client
+	// disconnected before processing finished, which would silently drop results.
 	if jobID != "" && s.deps.AIJobStore != nil {
 		status := domain.TaskStatusDone
 		if jobCtx.Err() != nil {
@@ -321,7 +323,7 @@ func (s *Server) handleAdminTextGenChapterNames(w http.ResponseWriter, r *http.R
 		resultsJSON, _ := json.Marshal(allResults)
 		finalPayload := fmt.Sprintf(`{"pattern":%q,"slug":%q,"results":%s}`,
 			req.Pattern, req.Slug, string(resultsJSON))
-		_ = s.deps.AIJobStore.UpdateAIJob(r.Context(), jobID, map[string]any{
+		_ = s.deps.AIJobStore.UpdateAIJob(context.Background(), jobID, map[string]any{
 			"status":     string(status),
 			"items_done": chaptersDone,
 			"finished":   time.Now().Format(time.RFC3339),

ui/src/routes/admin/ai-jobs/+page.server.ts

@@ -6,8 +6,7 @@ export type { AIJob };
 
 export const load: PageServerLoad = async () => {
 	// Parent layout already guards admin role.
-	// Stream jobs so navigation is instant; list populates a moment later.
-	const jobs = listAIJobs().catch((e): AIJob[] => {
+	const jobs = await listAIJobs().catch((e): AIJob[] => {
 		log.warn('admin/ai-jobs', 'failed to load ai jobs', { err: String(e) });
 		return [];
 	});

ui/src/routes/admin/ai-jobs/+page.svelte

@@ -9,9 +9,9 @@
 
 	let jobs = $state<AIJob[]>([]);
 
-	// Resolve streamed promise on load and on server reloads (invalidateAll)
+	// data.jobs is a plain AIJob[] (resolved on server); re-sync on invalidateAll
 	$effect(() => {
-		data.jobs.then((resolved) => { jobs = resolved; });
+		jobs = data.jobs;
 	});
 
 	// ── Live-poll while any job is in-flight ─────────────────────────────────────

ui/src/routes/api/translation/[slug]/[n]/+server.ts

@@ -23,9 +23,12 @@ export const GET: RequestHandler = async ({ params, url }) => {
 		return new Response(null, { status: res.status });
 	}
 	const data = await res.json();
-	return new Response(JSON.stringify(data), {
-		headers: { 'Content-Type': 'application/json' }
-	});
+	const headers: Record<string, string> = { 'Content-Type': 'application/json' };
+	// Forward the immutable cache header from the backend so browsers and CDNs
+	// can cache translated chapter content without hitting MinIO on every load.
+	const cc = res.headers.get('Cache-Control');
+	if (cc) headers['Cache-Control'] = cc;
+	return new Response(JSON.stringify(data), { headers });
 };
 
 export const POST: RequestHandler = async ({ params, url, locals }) => {