feat(data): add usage gate thresholds and task run model column

Adds AppSettings.UsageGateFiveHourPct/UsageGateSevenDayPct (defaults
80/90, clamped 0..100 in UpdateAsync) and a nullable TaskRunEntity.Model
column, laying the data foundation for the usage monitor. No worker/UI
changes.

src/ClaudeDo.Data/Configuration/AppSettingsEntityConfiguration.cs

@@ -47,6 +47,11 @@ public class AppSettingsEntityConfiguration : IEntityTypeConfiguration<AppSettin
         builder.Property(s => s.SessionSkills).HasColumnName("session_skills");
         builder.Property(s => s.ModelPresets).HasColumnName("model_presets");
 
+        builder.Property(s => s.UsageGateFiveHourPct)
+            .HasColumnName("usage_gate_five_hour_pct").IsRequired().HasDefaultValue(80);
+        builder.Property(s => s.UsageGateSevenDayPct)
+            .HasColumnName("usage_gate_seven_day_pct").IsRequired().HasDefaultValue(90);
+
         builder.HasData(new AppSettingsEntity { Id = AppSettingsEntity.SingletonId });
     }
 }

src/ClaudeDo.Data/Configuration/TaskRunEntityConfiguration.cs

@@ -27,6 +27,7 @@ public class TaskRunEntityConfiguration : IEntityTypeConfiguration<TaskRunEntity
         builder.Property(r => r.LogPath).HasColumnName("log_path");
         builder.Property(r => r.StartedAt).HasColumnName("started_at");
         builder.Property(r => r.FinishedAt).HasColumnName("finished_at");
+        builder.Property(r => r.Model).HasColumnName("model");
 
         builder.HasOne(r => r.Task)
             .WithMany(t => t.Runs)