feat(stats): flip home Plays card live (Phase 16.5)

Add TotalPlays + UniqueListeners to HomeStatsDto, composed at
StatsController from IEventService (no migration). Card reads via
existing persistent-state-bridged round-trip.

DeepDrftData/Repositories/EventRepository.cs

@@ -83,6 +83,16 @@ public class EventRepository
         }
     }
 
+    /// <summary>
+    /// Site-wide total plays: the sum of every counter's three bucket columns across all rows (Phase 16
+    /// §5). Sums the mapped columns directly rather than <see cref="PlayCounter.TotalPlays"/>, which is an
+    /// EF-ignored computed property and so not translatable. An empty counter table sums to 0 (the home
+    /// card's expected reading until the telemetry migration is applied).
+    /// </summary>
+    public Task<long> CountTotalPlaysAsync(CancellationToken ct = default)
+        => _context.PlayCounters
+            .SumAsync(c => c.PartialCount + c.SampledCount + c.CompleteCount, ct);
+
     /// <summary>
     /// Count distinct non-null anon ids across every play event (Phase 16 §3 / §4.2 — the all-time
     /// unique-listener metric, D3). Null anon ids (events where the listener sent no token, or storage