Fix: Prevent activity tracker errors from blocking checkout

Problem: Activity tracker DNS errors (littleshop-admin:8080) were blocking
checkout flow, preventing shipping address prompt from showing.

Solution: Wrap activity tracking in try-catch with warning log.
Checkout flow continues even if activity tracking fails.

This ensures users can complete checkout even if analytics are unavailable.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

TeleBot/TeleBot/Handlers/CallbackHandler.cs

@@ -744,7 +744,9 @@ namespace TeleBot.Handlers
                 return;
             }
 
-            // Track checkout initiation
+            // Track checkout initiation (non-blocking)
+            try
+            {
                 await _activityTracker.TrackActivityAsync(
                     message.Chat,
                     ActivityTypes.Checkout,
@@ -752,6 +754,11 @@ namespace TeleBot.Handlers
                     null,
                     session.Cart.GetTotalAmount()
                 );
+            }
+            catch (Exception ex)
+            {
+                _logger.LogWarning(ex, "Failed to track checkout activity - continuing anyway");
+            }
 
             // Initialize order flow
             session.OrderFlow = new OrderFlowData