feat(ai): move the assistant to its own "Odin" sidebar page

Promote the AI chat from a dashboard widget to a dedicated page:
- new sidebar item "Odin" under the Přehled section, gated on ai.use, → /odin
- new /odin route + Odin page (reuses the assistant component, with a light
  ai.use guard)
- remove the widget from the dashboard
- rebrand the assistant header "Asistent" → "Odin" and give the thread more
  height now that it owns the page

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/admin/ui/navData.tsx

@@ -38,6 +38,22 @@ export const menuSections: MenuSection[] = [
           </svg>
         ),
       },
+      {
+        path: "/odin",
+        label: "Odin",
+        permission: "ai.use",
+        end: true,
+        icon: (
+          <svg
+            viewBox="0 0 24 24"
+            fill="none"
+            stroke="currentColor"
+            strokeWidth="2"
+          >
+            <path d="M21 11.5a8.38 8.38 0 0 1-.9 3.8 8.5 8.5 0 0 1-7.6 4.7 8.38 8.38 0 0 1-3.8-.9L3 21l1.9-5.7a8.38 8.38 0 0 1-.9-3.8 8.5 8.5 0 0 1 4.7-7.6 8.38 8.38 0 0 1 3.8-.9h.5a8.48 8.48 0 0 1 8 8v.5z" />
+          </svg>
+        ),
+      },
     ],
   },
   {