feat(api): auto-activate streak freeze on inactive day (#108)

src/Orbit.Api/Extensions/ServiceCollectionExtensions.cs

@@ -345,6 +345,7 @@ public static WebApplicationBuilder AddOrbitInfrastructure(this WebApplicationBu
         builder.Services.AddHostedService<SlipAlertSchedulerService>();
         builder.Services.AddHostedService<AccountDeletionService>();
         builder.Services.AddHostedService<HabitDueDateAdvancementService>();
+        builder.Services.AddHostedService<StreakFreezeAutoActivationService>();
         builder.Services.AddHostedService<DataEncryptionMigrationService>();
         builder.Services.AddHostedService<SyncCleanupService>();
         builder.Services.AddHostedService<CalendarAutoSyncService>();

src/Orbit.Domain/Entities/SentStreakFreezeAlert.cs

@@ -0,0 +1,22 @@
+using Orbit.Domain.Common;
+
+namespace Orbit.Domain.Entities;
+
+public class SentStreakFreezeAlert : Entity
+{
+    public Guid UserId { get; private set; }
+    public DateOnly FrozenDate { get; private set; }
+    public DateTime SentAtUtc { get; private set; }
+
+    private SentStreakFreezeAlert() { }
+
+    public static SentStreakFreezeAlert Create(Guid userId, DateOnly frozenDate)
+    {
+        return new SentStreakFreezeAlert
+        {
+            UserId = userId,
+            FrozenDate = frozenDate,
+            SentAtUtc = DateTime.UtcNow
+        };
+    }
+}