feat: ILoginBonusService — JST day-bucketed claim + grant + DTO assembly

GrantIfDueAsync advances streak (1..15 cycle), grants the day's reward via
inventory tx, returns wire-shape DailyLoginBonus. IsDue helper for MyPage.

Also fixes GameConfigurationJsonbTests section-count (15→16) which was broken
since Task 3 added the LoginBonus [ConfigSection] but the assertion wasn't updated.

SVSim.EmulatedEntrypoint/Services/ILoginBonusService.cs

@@ -0,0 +1,22 @@
+using SVSim.Database.Services.Inventory;
+using SVSim.EmulatedEntrypoint.Models.Dtos;
+
+namespace SVSim.EmulatedEntrypoint.Services;
+
+/// <summary>
+/// Daily login bonus controller-facing API. Single entry point: called from
+/// /load/index inside the existing inventory transaction. Returns null when the viewer
+/// has already claimed today's bonus.
+/// </summary>
+public interface ILoginBonusService
+{
+    /// <summary>
+    /// If due, advances <c>tx.Viewer.LoginBonusStreak</c> + <c>LastLoginBonusClaimedAt</c>,
+    /// grants the day's reward via <paramref name="tx"/>, and returns the populated wire
+    /// DTO. If not due, returns null and leaves viewer state untouched.
+    /// </summary>
+    Task<DailyLoginBonus?> GrantIfDueAsync(IInventoryTransaction tx, CancellationToken ct = default);
+
+    /// <summary>Read-only "would GrantIfDueAsync emit a bonus right now?" — for MyPage flag.</summary>
+    bool IsDue(SVSim.Database.Models.Viewer viewer);
+}