Migrate omsorgapp to browser SPA, add Docker/CI build setup

- omsorgapp: drop Electron, run as a plain Vite/React browser app; refresh
  token moves to an HttpOnly cookie (omsorgCore), CORS added for the new
  browser origin, document download/preview switched to Blob-based browser
  APIs.
- Add Dockerfiles for omsorgCore, omsorgapp, and omsorgWeb, a docker-compose.yml
  wiring Postgres/MySQL/all three apps together, and a Gitea Actions workflow
  that builds and pushes images to the repo's container registry on push to
  main and on version tags.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

omsorgWeb/mitarbeiter-app/lib/layout.php

@@ -35,6 +35,16 @@ function layout_start(string $title, string $currentPage = 'dashboard'): void {
       <a href="dashboard.php" class="<?= $currentPage === 'dashboard' ? 'active' : '' ?>">
         <span class="nav-icon">⊞</span><span class="nav-label"> Dashboard</span>
       </a>
+      <?php if (has_permission('Absences', 'View')): ?>
+        <a href="urlaubsantrag.php" class="<?= $currentPage === 'urlaubsantrag' ? 'active' : '' ?>">
+          <span class="nav-icon">🗓</span><span class="nav-label"> Urlaub &amp; Abwesenheit</span>
+        </a>
+      <?php endif; ?>
+      <?php if (has_permission('TimeEntries', 'View')): ?>
+        <a href="stundenerfassung.php" class="<?= $currentPage === 'stundenerfassung' ? 'active' : '' ?>">
+          <span class="nav-icon">⏱</span><span class="nav-label"> Zeiterfassung</span>
+        </a>
+      <?php endif; ?>
       <a href="settings.php" class="<?= $currentPage === 'settings' ? 'active' : '' ?>">
         <span class="nav-icon">⚙</span><span class="nav-label"> Einstellungen</span>
       </a>