feat: Implement Scheduler Worker Options and Planner Loop

- Added `SchedulerWorkerOptions` class to encapsulate configuration for the scheduler worker.
- Introduced `PlannerBackgroundService` to manage the planner loop, fetching and processing planning runs.
- Created `PlannerExecutionService` to handle the execution logic for planning runs, including impact targeting and run persistence.
- Developed `PlannerExecutionResult` and `PlannerExecutionStatus` to standardize execution outcomes.
- Implemented validation logic within `SchedulerWorkerOptions` to ensure proper configuration.
- Added documentation for the planner loop and impact targeting features.
- Established health check endpoints and authentication mechanisms for the Signals service.
- Created unit tests for the Signals API to ensure proper functionality and response handling.
- Configured options for authority integration and fallback authentication methods.

src/StellaOps.Cli/Configuration/StellaOpsCliOptions.cs

@@ -11,6 +11,8 @@ public sealed class StellaOpsCliOptions
 
     public string BackendUrl { get; set; } = string.Empty;
 
+    public string ConcelierUrl { get; set; } = string.Empty;
+
     public string ScannerCacheDirectory { get; set; } = "scanners";
 
     public string ResultsDirectory { get; set; } = "results";