Add movie runtime, bulk OMDb refresh, and first-time setup

- Add runtime field to Movie model and display formatted duration (e.g., 2h 22min) on movie cards
- Add bulk "Refresh OMDb" button in admin panel for selected movies
- Add runtime field to movie edit modal in admin panel
- Implement first-time setup flow: show admin creation form on login page when no admin exists
- Block registration page until initial setup is complete

Co-Authored-By: Claude Opus 4.5 <[email protected]>

public/register.html

@@ -40,7 +40,20 @@
 </button>
 
 <div class="container d-flex justify-content-center align-items-center vh-100">
-  <div class="card p-4" style="max-width: 400px;">
+  <!-- Setup needed banner (hidden by default) -->
+  <div id="setup-needed-card" class="card p-4 d-none" style="max-width: 400px;">
+    <div class="text-center mb-4">
+      <img src="img/logo.png" class="logo-invert" style="width: 80%;" alt="Pool Oscars">
+    </div>
+    <div class="alert alert-warning mb-3">
+      <strong>Configuration requise</strong><br>
+      L'application doit d'abord être configurée par un administrateur.
+    </div>
+    <a href="/" class="btn btn-primary w-100">Aller à la page de configuration</a>
+  </div>
+
+  <!-- Normal registration card -->
+  <div id="register-card" class="card p-4" style="max-width: 400px;">
     <div class="text-center mb-4">
       <img src="img/logo.png" class="logo-invert" style="width: 80%;" alt="Pool Oscars">
     </div>