refactor: Extract ProfileWorker into modular components

- Create ProfileWorker namespace with 4 separate components
- ProfileWorker.cs: BackgroundService orchestrator with IOptions support
- ProfileWorkerOptions.cs: Configuration model with validation
- ProfileCache.cs: Thread-safe cache using composition pattern
- DependencyInjection.cs: Service registration with IValidateOptions

Benefits:
- Separation of concerns (orchestration, config, state, DI)
- IOptions pattern for appsettings.json configuration
- Startup validation for configuration errors
- Better testability and maintainability

ECMJobRunner.WebCron/ProfileWorker/DependencyInjection.cs

@@ -0,0 +1,42 @@
+using Microsoft.Extensions.Options;
+
+namespace ECMJobRunner.WebCron.ProfileWorker;
+
+public static class DependencyInjection
+{
+    public static IServiceCollection AddProfileWorker(this IServiceCollection services, IConfiguration configuration)
+    {
+        // Configure ProfileWorker options from appsettings.json
+        services.Configure<ProfileWorkerOptions>(
+            configuration.GetSection(ProfileWorkerOptions.SectionName));
+
+        // Validate options at startup
+        services.AddSingleton<IValidateOptions<ProfileWorkerOptions>, ProfileWorkerOptionsValidator>();
+
+        services.AddHostedService<ProfileWorker>();
+        services.AddSingleton<ProfileCache>();
+        services.AddScoped<ProfileWork>();
+        return services;
+    }
+}
+
+/// <summary>
+/// Validates ProfileWorkerOptions configuration at startup.
+/// </summary>
+internal class ProfileWorkerOptionsValidator : IValidateOptions<ProfileWorkerOptions>
+{
+    public ValidateOptionsResult Validate(string? name, ProfileWorkerOptions options)
+    {
+        if (options.IntervalMS <= 0)
+        {
+            return ValidateOptionsResult.Fail("ProfileWorker:IntervalMs must be greater than 0");
+        }
+
+        if (options.IntervalMS < 100)
+        {
+            return ValidateOptionsResult.Fail("ProfileWorker:IntervalMs should be at least 100ms to avoid excessive CPU usage");
+        }
+
+        return ValidateOptionsResult.Success;
+    }
+}