fix: ajouter liens navigation vers interface admin regles

- Lien sidebar base.html : "Regles metier" sous "Referentiels"
- Lien croise admin_referentiels.html → regles
- Boutons dashboard : "Gerer les referentiels" + "Regles metier"

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/viewer/templates/base.html

@@ -415,6 +415,7 @@
     <a href="/dim" class="sidebar-link">&#127973; Synth&egrave;se DIM</a>
     <a href="/cpam" class="sidebar-link">&#9888; Contr&ocirc;les UCR</a>
     <a href="/admin/referentiels" class="sidebar-link">&#128218; R&eacute;f&eacute;rentiels</a>
+    <a href="/admin/rules" class="sidebar-link">&#9881; R&egrave;gles m&eacute;tier</a>
   </nav>
   <div class="sidebar-search">
     <input type="text" id="sidebar-search" placeholder="Rechercher un dossier…" autocomplete="off">