Enhance SignalR Redis backplane configuration with robust connection options

- Added detailed connection options for StackExchange.Redis to improve SignalR backplane reliability.
- Implemented retry logic and connection settings to handle temporary Redis unavailability.
- Updated logging to provide clearer feedback on configuration success or failure, including stack trace information for error handling.
- Ensured fallback to single-instance mode when Redis is not configured, enhancing application resilience.

src/Managing.Api/Program.cs

@@ -30,6 +30,7 @@ using Serilog.Sinks.Elasticsearch;
 using OpenApiSecurityRequirement = Microsoft.OpenApi.Models.OpenApiSecurityRequirement;
 using OpenApiSecurityScheme = NSwag.OpenApiSecurityScheme;
 using DotNetEnv;
+using StackExchange.Redis;
 
 // Optionally load .env file if it exists (primarily for Vibe Kanban worktrees)
 // This is optional - if no .env file exists, the app will use system env vars and appsettings.json
@@ -474,18 +475,42 @@ if (!string.IsNullOrWhiteSpace(redisConnectionString))
     try
     {
         Console.WriteLine($"✅ Configuring SignalR with Redis backplane");
-        signalRBuilder.AddStackExchangeRedis(redisConnectionString, options =>
+        
+        // Parse and configure connection options properly
+        // This ensures Redis backplane works without sticky sessions by storing connection state in Redis
+        var connectionOptions = ConfigurationOptions.Parse(redisConnectionString);
+        
+        // CRITICAL: These settings allow Redis backplane to work without sticky sessions
+        connectionOptions.AbortOnConnectFail = false; // Don't fail if Redis is temporarily unavailable
+        connectionOptions.ConnectTimeout = 10000; // 10 second timeout
+        connectionOptions.ConnectRetry = 5; // Retry 5 times
+        connectionOptions.KeepAlive = 60; // Keep connection alive
+        connectionOptions.SyncTimeout = 5000;
+        connectionOptions.AsyncTimeout = 5000;
+        connectionOptions.ReconnectRetryPolicy = new ExponentialRetry(1000, 10000); // Exponential backoff: 1s to 10s
+        
+        // Convert ConfigurationOptions back to connection string format with all settings
+        var configuredConnectionString = connectionOptions.ToString();
+        
+        signalRBuilder.AddStackExchangeRedis(configuredConnectionString, options =>
         {
             // Configure channel prefix for SignalR messages
             options.Configuration.ChannelPrefix = "managing-signalr";
         });
+        
+        Console.WriteLine($"✅ SignalR Redis backplane configured successfully with retry logic");
     }
     catch (Exception ex)
     {
         Console.WriteLine($"⚠️  Failed to configure SignalR Redis backplane: {ex.Message}");
+        Console.WriteLine($"⚠️  Stack trace: {ex.StackTrace}");
         Console.WriteLine("SignalR will work in single-instance mode only");
     }
 }
+else
+{
+    Console.WriteLine("ℹ️  Redis not configured - SignalR running in single-instance mode");
+}
 
 builder.Services.AddScoped<IJwtUtils, JwtUtils>();