Improve ProfileWorker health-check logic and initialization

Refactor the `ProfileWorker` class to enhance health-check handling, including support for an uninitialized state. The `_lastSuccessfulRun` field was changed to a nullable `DateTime?` to represent when the service has not yet completed its first successful run.

Introduce a new health state, **Degraded (Initializing)**, to indicate the service is starting up. Update the `CheckHealthAsync` method to handle this state and return a `HealthCheckResult.Degraded` with relevant metadata.

Refine health-check logic to safely access `_lastSuccessfulRun.Value` only when initialized. Update documentation to clarify health status conditions and retain adaptive multiplier logic for detecting issues based on interval length.

Enhance `HealthCheckResult` metadata with additional details, including `LastSuccessfulRun`, time since last success, and consecutive failures. Improve comments and descriptions for better clarity.

ECMJobRunner.WebCron/ProfileWorker/ProfileWorker.cs

@@ -20,6 +20,7 @@ namespace ECMJobRunner.WebCron.ProfileWorker;
 /// </list>
 /// Health states (with adaptive thresholds):
 /// <list type="bullet">
+/// <item><description><b>Degraded (Initializing)</b>: Service starting up, waiting for first successful run</description></item>
 /// <item><description><b>Healthy</b>: Recent successful run with no failures</description></item>
 /// <item><description><b>Degraded</b>: 1+ consecutive failures but within time threshold</description></item>
 /// <item><description><b>Unhealthy</b>: No success within adaptive threshold (3x interval for fast intervals &lt;10s, 1.5x for slower intervals)</description></item>
@@ -35,7 +36,7 @@ public class ProfileWorker(
     private readonly ProfileWorkerOptions _options = Options.Value;
 
     // Health check state
-    private DateTime _lastSuccessfulRun = DateTime.UtcNow;
+    private DateTime? _lastSuccessfulRun = null; // null = not run yet
     private int _consecutiveFailures = 0;
     private Exception? _lastException = null;
 
@@ -107,13 +108,14 @@ public class ProfileWorker(
     /// A <see cref="HealthCheckResult"/> indicating the current health status:
     /// <list type="bullet">
     /// <item><description><see cref="HealthStatus.Healthy"/> - Service running normally</description></item>
-    /// <item><description><see cref="HealthStatus.Degraded"/> - Recent failures but still operational</description></item>
+    /// <item><description><see cref="HealthStatus.Degraded"/> - Recent failures but still operational, or service initializing</description></item>
     /// <item><description><see cref="HealthStatus.Unhealthy"/> - No successful run for extended period</description></item>
     /// </list>
     /// </returns>
     /// <remarks>
     /// Health determination logic:
     /// <list type="number">
+    /// <item><description><b>Degraded (Initializing)</b>: Service has not completed its first successful run yet</description></item>
     /// <item><description><b>Unhealthy</b>: Time since last success exceeds adaptive threshold (3x interval for fast intervals &lt;10s, 1.5x for slower intervals)</description></item>
     /// <item><description><b>Degraded</b>: 1+ consecutive failures within time threshold</description></item>
     /// <item><description><b>Healthy</b>: Recent successful run with no failures</description></item>
@@ -124,7 +126,32 @@ public class ProfileWorker(
         HealthCheckContext context, 
         CancellationToken cancellationToken = default)
     {
-        var timeSinceLastSuccess = DateTime.UtcNow - _lastSuccessfulRun;
+        // Service hasn't completed its first successful run yet
+        if (_lastSuccessfulRun == null)
+        {
+            var data = new Dictionary<string, object>
+            {
+                ["Status"] = "Initializing",
+                ["ConsecutiveFailures"] = _consecutiveFailures,
+                ["IntervalMS"] = _options.IntervalMS
+            };
+
+            if (_lastException != null)
+            {
+                data["LastException"] = _lastException.Message;
+            }
+
+            // Degraded during initialization (not unhealthy, service is starting up)
+            return Task.FromResult(HealthCheckResult.Degraded(
+                _consecutiveFailures > 0 
+                    ? $"ProfileWorker initializing with {_consecutiveFailures} failure(s)"
+                    : "ProfileWorker is initializing, waiting for first successful run",
+                _lastException,
+                data
+            ));
+        }
+
+        var timeSinceLastSuccess = DateTime.UtcNow - _lastSuccessfulRun.Value;
         
         // Adaptive multiplier: 3x for fast intervals (<10s), 1.5x for slower intervals
         // This ensures faster problem detection when using longer intervals (e.g., 60s)
@@ -136,7 +163,7 @@ public class ProfileWorker(
         {
             var data = new Dictionary<string, object>
             {
-                ["LastSuccessfulRun"] = _lastSuccessfulRun,
+                ["LastSuccessfulRun"] = _lastSuccessfulRun.Value,
                 ["TimeSinceLastSuccess"] = timeSinceLastSuccess,
                 ["ConsecutiveFailures"] = _consecutiveFailures,
                 ["IntervalMS"] = _options.IntervalMS,
@@ -156,12 +183,12 @@ public class ProfileWorker(
             ));
         }
 
-        // Degraded: 1-2 consecutive failures but within time limit
+        // Degraded: 1+ consecutive failures but within time limit
         if (_consecutiveFailures > 0)
         {
             var data = new Dictionary<string, object>
             {
-                ["LastSuccessfulRun"] = _lastSuccessfulRun,
+                ["LastSuccessfulRun"] = _lastSuccessfulRun.Value,
                 ["ConsecutiveFailures"] = _consecutiveFailures
             };
 
@@ -177,7 +204,7 @@ public class ProfileWorker(
             "ProfileWorker is running normally",
             new Dictionary<string, object>
             {
-                ["LastSuccessfulRun"] = _lastSuccessfulRun
+                ["LastSuccessfulRun"] = _lastSuccessfulRun.Value
             }
         ));
     }