test(form-builder): IDOR-class route-level security for form-failures admin (WS-6)

RFC §4 V3 compliance — cross-tenant access to FormSubmissionActionFailure
endpoints returns 404, not 403, to prevent resource-existence
enumeration. The FormSubmissionActionFailurePolicy is the single tenant
gate; these tests assert the route-level integration end-to-end.

Production-code finding (in scope per "security gaps zijn altijd urgent"):
the orgIndex endpoint had a real IDOR gap. Original implementation called
`Gate::authorize('viewAny', ...)` which permits any org_admin in any org,
then filtered the result set by the URL's `{organisation}` param. orgB's
admin hitting `/organisations/{orgA}/form-failures` would get back orgA's
failures — leakage.

Fix:
- New policy method `viewAnyInOrganisation(User, Organisation)` that
  requires super_admin OR org_admin on THIS specific organisation.
- Controller `orgIndex` calls `authorizeViewAnyInOrgOrNotFound()` which
  translates a denied policy → 404 (matches the show/retry/resolve/dismiss
  pattern).
- viewAny on the class level stays as the platformIndex gate (super_admin
  + any-org_admin enumeration is acceptable on the platform endpoint
  because the role middleware already restricts to super_admin).

Test coverage (24 tests, all passing):
- 5 org-scoped endpoints × cross-tenant scenarios (all return 404)
- 5 platform endpoints × role-class scenarios (org_admin gets 403, never 404)
- Edge cases: soft-deleted parent submission, invalid ULID format,
  non-existent ID, unauthenticated, authenticated-without-role on org

The 403 vs 404 distinction matters: role-gated endpoints return 403
(auth-class — "not allowed in this room"); ownership-gated endpoints
return 404 (IDOR-class — "this room doesn't exist for you").

Refs: RFC-WS-6.md §4 V3, ARCH-BINDINGS.md §8.2 (Task 3 of this session)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

api/app/Policies/FormBuilder/FormSubmissionActionFailurePolicy.php

@@ -32,6 +32,25 @@ final class FormSubmissionActionFailurePolicy
             ->exists();
     }
 
+    /**
+     * RFC V3 — tenant gate for the org-scoped index endpoint.
+     * The caller must be super_admin OR an org_admin on THIS specific
+     * organisation; without this check the broader `viewAny` would let
+     * orgB's admin enumerate orgA's failure rows via orgA's URL.
+     * Denied → controller translates to 404 to keep the IDOR contract.
+     */
+    public function viewAnyInOrganisation(User $user, Organisation $organisation): bool
+    {
+        if ($user->hasRole('super_admin')) {
+            return true;
+        }
+
+        return $organisation->users()
+            ->where('user_id', $user->id)
+            ->wherePivot('role', 'org_admin')
+            ->exists();
+    }
+
     public function view(User $user, FormSubmissionActionFailure $failure): bool
     {
         return $this->canAccess($user, $failure);