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/Models/AppSettingsEntity.cs

@@ -34,4 +34,8 @@ public sealed class AppSettingsEntity
     // JSON array of ModelPreset rows (model → effort + max turns). Supplies the global effort and
     // turn defaults per model; list-/task-level max-turns overrides still win. Null = ship defaults.
     public string? ModelPresets { get; set; }
+
+    // Percentage of the 5h/7d Claude usage window at which the autonomous queue pauses. 0 = gate off.
+    public int UsageGateFiveHourPct { get; set; } = 80;
+    public int UsageGateSevenDayPct { get; set; } = 90;
 }

src/ClaudeDo.Data/Models/TaskRunEntity.cs

@@ -18,6 +18,7 @@ public sealed class TaskRunEntity
     public string? LogPath { get; set; }
     public DateTime? StartedAt { get; set; }
     public DateTime? FinishedAt { get; set; }
+    public string? Model { get; set; }
 
     // Navigation property
     public TaskEntity Task { get; set; } = null!;