Add authentication and improve server side configuration

RemoteExec.Server/appsettings.json

@@ -5,5 +5,49 @@
       "Microsoft.AspNetCore": "Warning"
     }
   },
-  "AllowedHosts": "*"
+  "AllowedHosts": "*",
+  
+  // Authentication configuration
+  "Authentication": {
+    // List of API keys for authenticating clients
+    // Each entry should contain key identification and validation information
+    "ApiKeys": [
+      // Example:
+      // {
+      //   "Key": "your-secret-api-key-here",
+      //   "Name": "Client1",
+      //   "Enabled": true
+      // }
+    ]
+  },
+  
+  // Remote execution configuration
+  "Execution": {
+    // Maximum number of tasks that can execute concurrently on the server
+    // null = uses Environment.ProcessorCount * 2 (default)
+    // Increase for CPU-light tasks, decrease for resource-intensive operations
+    "MaxConcurrentTasks": null,
+    
+    // Timeout in seconds for loading assemblies from clients
+    // If a client doesn't respond with assembly bytes within this time, the request fails
+    // Default: 30 seconds
+    "AssemblyLoadTimeoutSeconds": 30
+  },
+  
+  // Server metrics broadcasting configuration
+  "Metrics": {
+    // Minimum CPU usage difference (in percentage points) required to trigger a metrics broadcast
+    // Lower values = more frequent updates, higher values = less network traffic
+    // Default: 1.0 (1%)
+    "CpuDifferenceThreshold": 1.0,
+    
+    // Minimum memory usage difference (in bytes) required to trigger a metrics broadcast
+    // Default: 10485760 (10 MB)
+    "MemoryDifferenceThreshold": 10485760,
+    
+    // Interval in milliseconds between metrics broadcasts to all connected clients
+    // Lower values = more real-time updates, higher values = less server load
+    // Default: 5000 (5 seconds)
+    "BroadcastIntervalMs": 5000
+  }
 }