feat: implement Blazor web interface for GM session management

- Created GmRelay.Web project (Blazor Server)
- Created GmRelay.Shared library for domain models and rendering
- Refactored GmRelay.Bot to use the Shared library
- Integrated Telegram Login widget with server-side HMAC verification
- Added Dashboard, Group Details, and Edit Session pages
- Enabled bot notifications and in-place message updates from web actions
- Updated .NET Aspire orchestration and Docker Compose configuration

src/GmRelay.Shared/Domain/MoscowTime.cs

@@ -0,0 +1,34 @@
+namespace GmRelay.Shared.Domain;
+
+public static class MoscowTime
+{
+    private static readonly TimeSpan MoscowOffset = TimeSpan.FromHours(3);
+
+    public static DateTimeOffset Now => DateTimeOffset.UtcNow.ToOffset(MoscowOffset);
+
+    public static DateTimeOffset ToMoscow(this DateTimeOffset utc) => utc.ToOffset(MoscowOffset);
+
+    public static string FormatMoscow(this DateTimeOffset utc)
+        => utc.ToOffset(MoscowOffset).ToString("d MMMM yyyy, HH:mm", System.Globalization.CultureInfo.GetCultureInfo("ru-RU"));
+
+    public static DateTime ToMoscow(this DateTime utcDt) => utcDt.Add(MoscowOffset);
+
+    public static string FormatMoscow(this DateTime utcDt)
+        => utcDt.Add(MoscowOffset).ToString("d MMMM yyyy, HH:mm", System.Globalization.CultureInfo.GetCultureInfo("ru-RU"));
+
+    public static string FormatMoscowShort(this DateTime utcDt)
+        => utcDt.Add(MoscowOffset).ToString("dd.MM");
+
+    public static bool TryParseMoscow(string text, out DateTimeOffset utcTime)
+    {
+        if (DateTime.TryParseExact(text, new[] { "dd.MM.yyyy HH:mm", "dd.MM.yyyy H:mm", "d.MM.yyyy HH:mm" }, 
+            System.Globalization.CultureInfo.InvariantCulture, System.Globalization.DateTimeStyles.None, out var localDt))
+        {
+            utcTime = new DateTimeOffset(localDt, MoscowOffset).ToUniversalTime();
+            return true;
+        }
+
+        utcTime = default;
+        return false;
+    }
+}

src/GmRelay.Shared/Domain/RsvpStatus.cs

@@ -0,0 +1,8 @@
+namespace GmRelay.Shared.Domain;
+
+public static class RsvpStatus
+{
+    public const string Pending = "Pending";
+    public const string Confirmed = "Confirmed";
+    public const string Declined = "Declined";
+}

src/GmRelay.Shared/Domain/SessionStatus.cs

@@ -0,0 +1,9 @@
+namespace GmRelay.Shared.Domain;
+
+public static class SessionStatus
+{
+    public const string Planned = "Planned";
+    public const string ConfirmationSent = "ConfirmationSent";
+    public const string Confirmed = "Confirmed";
+    public const string Cancelled = "Cancelled";
+}