feat: add yearly summary page with navigation and formatting improvements

Formatting/DurationFormatter.cs

@@ -0,0 +1,37 @@
+namespace WorkTracker.Formatting;
+
+public static class DurationFormatter
+{
+    public static string FormatHours(decimal value, bool blankWhenZero = false)
+    {
+        var totalMinutes = (int)Math.Round(value * 60m, MidpointRounding.AwayFromZero);
+        if (totalMinutes == 0)
+        {
+            return blankWhenZero ? string.Empty : "0";
+        }
+
+        var sign = totalMinutes < 0 ? "-" : string.Empty;
+        totalMinutes = Math.Abs(totalMinutes);
+
+        var hours = totalMinutes / 60;
+        var minutes = totalMinutes % 60;
+        return minutes == 0
+            ? $"{sign}{hours}"
+            : $"{sign}{hours}:{minutes:00}";
+    }
+
+    public static string FormatSignedHours(decimal value)
+    {
+        if (value > 0m)
+        {
+            return $"+{FormatHours(value)}";
+        }
+
+        if (value < 0m)
+        {
+            return $"-{FormatHours(Math.Abs(value))}";
+        }
+
+        return "0";
+    }
+}