[WI16] Fix Flink JobManager discovery - Use broader container name filter

Root cause: Docker container name filter was too strict
- Previous filter: "name=flink-jobmanager" only matched exact substring
- Aspire container names may have different patterns/prefixes
- Filter failed to find containers, returning no endpoint

Changes:
- Updated GetFlinkRestApiEndpointAsync() to use broader filter: "name=flink"
- Matches any container with "flink" in name, then validates port 8081 mapping
- Added diagnostic logging showing all Flink containers found
- More resilient discovery working with Aspire's container naming

This fixes Day01 health check failures by correctly discovering Flink JobManager endpoint.

Co-authored-by: devstress <30769729+devstress@users.noreply.github.com>

Author: Copilot

LearningCourse/LearningCourse.Common/DockerInfrastructure.cs

@@ -363,8 +363,10 @@ public static async Task<string> GetFlinkRestApiEndpointAsync()
     {
         try
         {
-            var flinkContainers = await RunDockerCommandAsync("ps --filter name=flink-jobmanager --format {{.Ports}}");
-            Console.WriteLine($"🔍 Flink JobManager port mappings: {flinkContainers.Trim()}");
+            // Use broader filter to match any Flink container (Aspire may use different naming patterns)
+            // Then validate by checking for port 8081 mapping (Flink JobManager REST API)
+            var flinkContainers = await RunDockerCommandAsync("ps --filter name=flink --format {{.Ports}}");
+            Console.WriteLine($"🔍 All Flink container port mappings: {flinkContainers.Trim()}");
 
             // Log docker ps after discovering Flink ports
             await LogDockerPsAsync("After Flink REST API Discovery");