Vorgaenge in der WebUI: entscheiden und Stellungnahme anfordern (#689, Stufe 3)

- /api/cases (offen/alle), /api/cases/{id}/decide, /api/cases/{id}/statement, /api/decisions
- Ansicht "Vorgaenge": offene Faelle mit Verlauf je Ebene (Lauf-Links), Frist und
  "Mensch gerufen"; Reiter Beschluesse mit Reichweite; Zaehler in der Seitenleiste
- Konzept Abschnitt 5: Umsetzung

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/ClawdDotNet.Manager.Web/wwwroot/index.html

@@ -124,6 +124,13 @@
           <span class="nav-label" data-i18n="nav.staging">Approvals</span>
           <span id="staging-badge" class="nav-badge" hidden>0</span>
         </a>
+        <a href="#/cases" class="nav-link" title="Cases" data-i18n-title="nav.cases">
+          <svg width="18" height="18" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="1.75">
+            <path d="M12 3v6 M8 7l4-4 4 4 M4 13h16v8H4z M9 17h6"/>
+          </svg>
+          <span class="nav-label" data-i18n="nav.cases">Cases</span>
+          <span id="faelle-badge" class="nav-badge" hidden>0</span>
+        </a>
         <a href="#/protokoll" class="nav-link" title="Logs" data-i18n-title="nav.logs">
           <svg width="18" height="18" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="1.75">
             <path d="M4 19.5A2.5 2.5 0 0 1 6.5 17H20 M6.5 2H20v20H6.5A2.5 2.5 0 0 1 4 19.5v-15A2.5 2.5 0 0 1 6.5 2z M8 7h8 M8 11h6"/>