fix(ingestion,frontend): show live counter immediately on run start

Two issues with the initial implementation:
- Counter only appeared after the first SSE event arrived (scholarProgress null
  kept the v-else static template showing until a scholar completed)
- First events were often dropped because the EventSource hadn't subscribed yet

Fix:
- Backend: emit an initial scholar_progress kickoff event (0/0/N) at the
  start of run_scholar_iteration so the frontend receives total early
- Frontend: gate on isLikelyRunning alone (not scholarProgress); use optional
  chaining with fallbacks so "0 / … visited · 0 finished" shows immediately
  when a run starts, before any SSE events arrive

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/pages/DashboardPage.vue

@@ -487,9 +487,9 @@ watch(
                     </div>
                     <p class="mt-2 text-sm text-secondary">
                       Started {{ formatDate(displayedLatestRun.start_dt) }}.
-                      <template v-if="runStatus.isLikelyRunning && runStatus.scholarProgress">
-                        {{ runStatus.scholarProgress.visited }} / {{ runStatus.scholarProgress.total }} visited
-                        · {{ runStatus.scholarProgress.finished }} finished
+                      <template v-if="runStatus.isLikelyRunning">
+                        {{ runStatus.scholarProgress?.visited ?? 0 }} / {{ runStatus.scholarProgress?.total ?? '…' }} visited
+                        · {{ runStatus.scholarProgress?.finished ?? 0 }} finished
                         · {{ displayedLatestRun.new_publication_count }} new publications.
                       </template>
                       <template v-else>