feat(workflow): document-wait task + 30-day timeout cancellation (S-10a, closes #102) (#105)

## What & why

S-10a, the **workflow/timeout spine** of the (split) document-upload slice: the registratie process
now parks at a **`WachtOpDocumenten`** user task with an **interrupting `P30D` boundary timer**. When
the documents arrive the task completes and the process continues into the diploma routing (S-13) →
Beoordelen; if the 30 days lapse, the timer cancels the wait, runs a `RegistratieVerlopen`
external-worker task, and the domain expires the aggregate to a new terminal status **`Verlopen`**.
Backend only — the real upload trigger (portal → BFF → ACL → Documenten API) is S-10b (#103).

Closes #102

Mechanism recorded in **ADR-0017**; opened as proposal #104. Mirrors the S-14 escalation
(boundary-timer + external-worker) and S-11 withdrawal (interrupting cancel) patterns.

## Definition of Done

- [x] Linked Gitea issue (above).
- [x] Failing test committed before the implementation (red→green pairs per layer).
- [x] Implementation makes the test pass.
- [x] Conventional Commits referencing the issue (`refs #102`).
- [ ] CI green — all Gitea Actions jobs (pending on this PR).
- [x] `docker compose up` health unaffected (no new services; deploy path unchanged).
- [x] Docs updated (ADR-0017, demo-script, BACKLOG split).
- [x] ADR added (`docs/architecture/adr-0017-document-wait-timeout-cancellation.md`).
- [x] Demo note in `docs/demo-script.md`.

## Notes for reviewers

- **Domain** (`Registration.Expire()` + `Verlopen`), **application** (`ExpireRegistrationWorker`),
  **infra** (`RegistratieVerlopenProcessor`/`Pump`, `IRegistratieVerlopenClient`, Flowable
  acquire/complete + `CompleteDocumentWaitAsync`) — the timeout counterpart to the OpenZaak/escalation
  worker trios; idempotent per §8.6.
- **BPMN** verified live against a `flowable-rest` probe: complete `WachtOpDocumenten` → routes to
  Beoordelen; fire the P30D timer → `RegistratieVerlopen` job (carrying `registrationId`) + the wait
  task cancelled. `verify-domain` exercises both branches in-stack (completes the wait in every existing
  block; fires the timer and asserts `Verlopen` in a new block).
- **Scope boundary:** on expiry the aggregate goes `Verlopen` and the process ends, but the ZGW *zaak*
  is not yet set to a cancellation status — that needs a new ACL method + statustype seeding and is
  folded into S-10b (noted in ADR-0017).
- `CompleteDocumentWaitAsync` is built and HTTP-tested here but not yet called from a domain endpoint;
  S-10b wires the upload trigger to it.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Reviewed-on: #105

services/domain/Big.Domain/Registration.cs

@@ -133,8 +133,24 @@ public sealed class Registration
         Status = RegistrationStatus.Ingetrokken;
     }
 
-    // A decision (or withdrawal) is only valid while the registration is still open (INGEDIEND or
-    // IN_BEHANDELING).
+    /// <summary>
+    /// Expire the registration — the 30-day document-wait timer fired before the required documents
+    /// were supplied, so the registratie process cancels the case (S-10a). Allowed while it is still
+    /// open (INGEDIEND or IN_BEHANDELING) and needs no zaak; a decided (INGESCHREVEN/AFGEWEZEN) or
+    /// withdrawn (INGETROKKEN) registration can no longer expire. Re-expiring one already
+    /// <see cref="RegistrationStatus.Verlopen"/> is a no-op — the worker job may be redelivered (§8.6).
+    /// </summary>
+    public void Expire()
+    {
+        if (Status == RegistrationStatus.Verlopen)
+            return;
+
+        RequireOpenForDecision(nameof(Expire));
+        Status = RegistrationStatus.Verlopen;
+    }
+
+    // A decision (or withdrawal, or expiry) is only valid while the registration is still open
+    // (INGEDIEND or IN_BEHANDELING).
     private void RequireOpenForDecision(string decision)
     {
         if (Status is not (RegistrationStatus.Ingediend or RegistrationStatus.InBehandeling))

services/domain/Big.Domain/RegistrationStatus.cs

@@ -21,4 +21,8 @@ public enum RegistrationStatus
 
     /// <summary>Withdrawn by the zorgprofessional before a decision (S-11). Terminal.</summary>
     Ingetrokken,
+
+    /// <summary>Lapsed: the required documents were not supplied within the 30-day window, so the
+    /// registratie process cancelled the case (S-10a). Terminal.</summary>
+    Verlopen,
 }