feat(viewer): add FreePackClaims owned collection for daily-free quota tracking

SVSim.Database/Models/ViewerFreePackClaim.cs

@@ -0,0 +1,15 @@
+using Microsoft.EntityFrameworkCore;
+
+namespace SVSim.Database.Models;
+
+/// <summary>
+/// One row per (viewer, free_gacha_campaign_id). Counts claims and remembers when the last one
+/// landed so the controller can gate the daily quota. Owned collection on <see cref="Viewer"/>.
+/// </summary>
+[Owned]
+public class ViewerFreePackClaim
+{
+    public int FreeGachaCampaignId { get; set; }
+    public int ClaimCount { get; set; }
+    public DateTime LastClaimedAt { get; set; }
+}