feat(bp): /battle_pass/info — service + controller + 3 tests

Also fixes BattlePassRepository.GetActiveSeasonAsync to use client-side
DateTimeOffset filtering (SQLite provider cannot translate DateTimeOffset
comparisons in LINQ WHERE/ORDER BY clauses).

SVSim.EmulatedEntrypoint/Services/IBattlePassService.cs

@@ -1,4 +1,5 @@
 using SVSim.EmulatedEntrypoint.Models.Dtos;
+using SVSim.EmulatedEntrypoint.Models.Dtos.BattlePass;
 
 namespace SVSim.EmulatedEntrypoint.Services;
 
@@ -7,5 +8,9 @@ public interface IBattlePassService
     /// <summary>Global level curve as wire-string dictionary; null if no levels seeded.</summary>
     Task<IReadOnlyDictionary<string, BattlePassLevel>?> GetLevelCurveAsync(CancellationToken ct);
 
-    // The Info / ItemList / Buy / AddPoints methods are added in later tasks (11, 12, 13, 14).
+    /// <summary>
+    /// /battle_pass/info payload. Returns null when no active season window covers <c>now</c>
+    /// (controller emits empty body in that case).
+    /// </summary>
+    Task<BattlePassInfoResponse?> GetInfoAsync(long viewerId, CancellationToken ct);
 }