fix: browser tab title uses page_title block — reflète le workspace actif

<title>FlowDeck</title> → <title>FlowDeck — {% block page_title %}Home{% endblock %}</title>

Maintenant l'onglet navigateur affiche:
- 'FlowDeck — Home' (page d'accueil)
- 'FlowDeck — bruno/flowdeck' (workspace Gitea)
- 'FlowDeck — Mon workspace local' (workspace local)

app/templates/base.html

@@ -3,7 +3,7 @@
 <head>
   <meta charset="UTF-8">
   <meta name="viewport" content="width=device-width, initial-scale=1.0">
-  <title>FlowDeck</title>
+  <title>FlowDeck — {% block page_title %}Home{% endblock %}</title>
   <link rel="icon" type="image/svg+xml" href="/static/favicon.svg">
   <link rel="stylesheet" href="/static/css/design-tokens.css?v=1.0">
   <link rel="stylesheet" href="/static/css/app.css?v=2.4.6">