feat(workflow): 14-day beoordeling escalation timer + hosted worker (S-14, refs #15)

Add a non-interrupting P14D boundary timer on the Beoordelen user task that fires
an external-worker task (BeoordelingEscaleren) to the escalation end; wire the
hosted BeoordelingEscalatiePump and register the escalation client/processor in DI.
On timeout the still-open beoordeling is reassigned to teamlead (ADR-0015).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

services/domain/Big.Infrastructure/BeoordelingEscalatiePump.cs

@@ -0,0 +1,49 @@
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
+using Microsoft.Extensions.Logging;
+
+namespace Big.Infrastructure;
+
+/// <summary>
+/// The hosted polling loop of the beoordeling-escalation worker (S-14, ADR-0015): on an interval it
+/// resolves a scoped <see cref="BeoordelingEscalatieProcessor"/> and asks it to drain the parked
+/// <c>BeoordelingEscaleren</c> jobs. A deliberately thin shell — all acquire/reassign/complete logic
+/// lives in the processor, which is unit-tested; this class only owns the timer, the per-tick scope,
+/// and loop resilience. Structurally identical to <see cref="OpenZaakJobPump"/>.
+/// </summary>
+public sealed class BeoordelingEscalatiePump(
+    IServiceScopeFactory scopeFactory,
+    FlowableOptions options,
+    ILogger<BeoordelingEscalatiePump> logger) : BackgroundService
+{
+    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
+    {
+        while (!stoppingToken.IsCancellationRequested)
+        {
+            try
+            {
+                using var scope = scopeFactory.CreateScope();
+                var processor = scope.ServiceProvider.GetRequiredService<BeoordelingEscalatieProcessor>();
+                await processor.PumpOnceAsync(options.MaxJobsPerPoll, stoppingToken);
+            }
+            catch (OperationCanceledException) when (stoppingToken.IsCancellationRequested)
+            {
+                break;
+            }
+            catch (Exception ex)
+            {
+                // A transient fault (e.g. Flowable briefly unreachable) must not kill the loop.
+                logger.LogError(ex, "BeoordelingEscaleren job poll failed; retrying after the poll interval.");
+            }
+
+            try
+            {
+                await Task.Delay(options.PollInterval, stoppingToken);
+            }
+            catch (OperationCanceledException) when (stoppingToken.IsCancellationRequested)
+            {
+                break;
+            }
+        }
+    }
+}