feat: add login hint on start page for unauthenticated users

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

templates/homepage/index.html.twig

@@ -34,6 +34,11 @@
                 <button type="submit" class="btn btn-primary btn-start">Commencer une partie</button>
             </form>
             <div class="start-loader" id="start-loader"></div>
+            {% if not app.user %}
+                <p class="start-login-hint">
+                    <a href="{{ path('app_login') }}">Connectez-vous</a> pour importer vos propres films
+                </p>
+            {% endif %}
             <script>
                 document.getElementById('start-form').addEventListener('submit', function () {
                     this.style.display = 'none';