feat(listsessions): add join/leave buttons for players

For non-managers /listsessions now shows player-friendly actions:
- ✅ Записаться <date> when not registered
- ✖️ Выйти <date> when already active
- ✖️ Выйти из ожидания <date> when waitlisted

Extend SessionListItemDto and the shared SQL query with IsUserActive
and IsUserWaitlisted flags so the renderer can choose the right button.
Update tests to cover all three player states.

tests/GmRelay.Bot.Tests/Features/Sessions/ListSessions/SessionListMessageRendererTests.cs

@@ -20,7 +20,9 @@ public sealed class SessionListMessageRendererTests
                 4,
                 3,
                 1,
-                true)
+                true,
+                false,
+                false)
         };
 
         var text = SessionListMessageRenderer.RenderText(sessions);
@@ -41,22 +43,83 @@ public sealed class SessionListMessageRendererTests
     }
 
     [Fact]
-    public void Render_ShouldHideManagerActions_WhenUserCannotManage()
+    public void Render_ShouldIncludeJoinAction_WhenPlayerIsNotRegistered()
     {
+        var sessionId = Guid.NewGuid();
         var sessions = new[]
         {
             new SessionListItemDto(
-                Guid.NewGuid(),
+                sessionId,
+                "Ravenloft",
+                new DateTime(2026, 5, 7, 16, 30, 0, DateTimeKind.Utc),
+                SessionStatus.Planned,
+                4,
+                3,
+                0,
+                false,
+                false,
+                false)
+        };
+
+        var actions = SessionListMessageRenderer.RenderActions(sessions);
+        var shortDate = new DateTime(2026, 5, 7, 16, 30, 0, DateTimeKind.Utc).FormatMoscowShort();
+
+        Assert.Single(actions);
+        Assert.Contains(actions, a => a.Payload == $"join_session:{sessionId}");
+        Assert.Contains(actions, a => a.Label == $"✅ Записаться {shortDate}");
+    }
+
+    [Fact]
+    public void Render_ShouldIncludeLeaveAction_WhenPlayerIsActive()
+    {
+        var sessionId = Guid.NewGuid();
+        var sessions = new[]
+        {
+            new SessionListItemDto(
+                sessionId,
+                "Ravenloft",
+                new DateTime(2026, 5, 7, 16, 30, 0, DateTimeKind.Utc),
+                SessionStatus.Planned,
+                4,
+                3,
+                0,
+                false,
+                true,
+                false)
+        };
+
+        var actions = SessionListMessageRenderer.RenderActions(sessions);
+        var shortDate = new DateTime(2026, 5, 7, 16, 30, 0, DateTimeKind.Utc).FormatMoscowShort();
+
+        Assert.Single(actions);
+        Assert.Contains(actions, a => a.Payload == $"leave_session:{sessionId}");
+        Assert.Contains(actions, a => a.Label == $"✖️ Выйти {shortDate}");
+    }
+
+    [Fact]
+    public void Render_ShouldIncludeLeaveWaitlistAction_WhenPlayerIsWaitlisted()
+    {
+        var sessionId = Guid.NewGuid();
+        var sessions = new[]
+        {
+            new SessionListItemDto(
+                sessionId,
                 "Ravenloft",
                 new DateTime(2026, 5, 7, 16, 30, 0, DateTimeKind.Utc),
                 SessionStatus.Planned,
                 4,
                 3,
                 1,
-                false)
+                false,
+                false,
+                true)
         };
 
         var actions = SessionListMessageRenderer.RenderActions(sessions);
-        Assert.Empty(actions);
+        var shortDate = new DateTime(2026, 5, 7, 16, 30, 0, DateTimeKind.Utc).FormatMoscowShort();
+
+        Assert.Single(actions);
+        Assert.Contains(actions, a => a.Payload == $"leave_session:{sessionId}");
+        Assert.Contains(actions, a => a.Label == $"✖️ Выйти из ожидания {shortDate}");
     }
 }