feat: Implement sidebar toggle functionality and enhance Monthly Timesheet summary view

Domain/MonthlyTimesheetModel.cs

@@ -0,0 +1,46 @@
+namespace WorkTracker.Domain;
+
+public sealed class MonthlyTimesheetModel
+{
+    public int Year { get; set; }
+
+    public int Month { get; set; }
+
+    public List<MonthlyTimesheetDayModel> Days { get; set; } = [];
+
+    public List<MonthlyTimesheetRowModel> Rows { get; set; } = [];
+}
+
+public sealed class MonthlyTimesheetDayModel
+{
+    public DateOnly Date { get; set; }
+
+    public bool IsWeekend { get; set; }
+
+    public bool IsHoliday { get; set; }
+
+    public bool IsClosure { get; set; }
+
+    public List<string> WorkUnitSummaries { get; set; } = [];
+
+    public List<string> EventSummaries { get; set; } = [];
+}
+
+public sealed class MonthlyTimesheetRowModel
+{
+    public string Key { get; set; } = string.Empty;
+
+    public string Label { get; set; } = string.Empty;
+
+    public MonthlyTimesheetValueFormat ValueFormat { get; set; }
+
+    public List<decimal?> DailyValues { get; set; } = [];
+
+    public decimal? Total { get; set; }
+}
+
+public enum MonthlyTimesheetValueFormat
+{
+    Hours = 0,
+    Days = 1
+}