feat(standup): standup automatique hier/aujourd'hui/blocages (issue #6)

format_standup_text + _standup_data (journal de la veille, focus
du jour, vieillissantes QA/Révision); page /standup copiable,
/api/standup; inclusion optionnelle au briefing ntfy
(KANBANTE_BRIEFING_INCLUDE_STANDUP).

app/templates/briefing.html

@@ -24,6 +24,7 @@
             <a href="/capture" class="nav-pill">⚡ Capture</a>
             <a href="/digest" class="nav-pill">🧠 Digest</a>
             <a href="/forecast" class="nav-pill">🔮 Prévisions</a>
+            <a href="/rules" class="nav-pill">⚙️ Règles</a>
             <a href="/wall" class="nav-pill">🖥️ Wallboard</a>
             <button type="button" class="nav-pill palette-trigger" title="Palette de commandes (Ctrl+K)">⌨️ Ctrl K</button>
         </nav>