feat: login time window rules (EPIC_000014)

- Implemented RuleManager and JSON storage
- Added background enforcement scheduler
- Added Web UI for rule management at /ui/rules
- Bumped version to 0.3.0

backend/templates/index.html

@@ -128,10 +128,16 @@
   <section id="userSection" class="panel-section hidden">
     <h3><i data-lucide="users"></i> Nutzerverwaltung</h3>
 
-    <button id="refreshUsersBtn" class="secondary small">
-      <i data-lucide="refresh-cw"></i>
-      Aktualisieren
-    </button>
+    <div style="display: flex; gap: 0.5rem; margin-bottom: 0.5rem;">
+        <button id="refreshUsersBtn" class="secondary small">
+          <i data-lucide="refresh-cw"></i>
+          Aktualisieren
+        </button>
+        <a href="/ui/rules" class="button secondary small">
+          <i data-lucide="clock"></i>
+          Regeln verwalten
+        </a>
+    </div>
 
     <table class="user-table mt-1">
       <thead>