fix(admin-rules-edit): accept /admin/procedural-events/{id}/edit in URL parser

Slice B.6 / S6 renamed the canonical edit URL from /admin/rules/{id}/edit
to /admin/procedural-events/{id}/edit. The backend handler + 301 redirect
landed, but the client-side regex in admin-rules-edit.ts:110 was missed —
it still only matches the legacy /admin/rules/.../edit shape. Result:
visiting the canonical URL from the list page shows 'Ungültige
Verfahrensschritt-ID in der URL.' even though the rule exists.

Fix: regex accepts both '/admin/procedural-events/{id}/edit' (canonical)
and '/admin/rules/{id}/edit' (legacy, kept for stale tabs / bookmarks
during the deprecation window).

m flagged 2026-05-27 17:57 on rule cc439590 (RoP.262.2, upc.inf.cfi).

frontend/src/client/admin-rules-edit.ts

@@ -106,8 +106,10 @@ function fmtDateTime(iso: string): string {
 }
 
 function parseRuleIDFromPath(): string {
-  // /admin/procedural-events/{uuid}/edit
-  const m = /^\/admin\/rules\/([^\/]+)\/edit\/?$/.exec(window.location.pathname);
+  // /admin/procedural-events/{uuid}/edit (canonical, post Slice B.6 rename)
+  // /admin/rules/{uuid}/edit (legacy, 301-redirected by the backend but
+  //   still matched here in case a stale tab or bookmark hits it).
+  const m = /^\/admin\/(?:procedural-events|rules)\/([^\/]+)\/edit\/?$/.exec(window.location.pathname);
   return m ? decodeURIComponent(m[1]) : "";
 }