ui(icons): replace colored emoji with modern single-color line icons (lucide-vue-next)

Add lucide-vue-next (stroke-based, single-color, currentColor) and swap emoji icons
across nav + all main views: Settings/LogOut (App), BarChart3/Users/Plus (Analytics),
LayoutDashboard (MyBoard), Sparkles/Users/Pencil (GroupEdit), Box/ListChecks/Paperclip/
PlusCircle/ArrowLeft (GroupBuilder), Target/ArrowLeft/Search (Chat/Personas/Training),
User/Lock/Globe (Settings), Users/UserPlus/Info (AdminUsers).
- Buttons become inline-flex for icon+text alignment.
- Icons inherit currentColor (single color, modern line style).
- Rebuild dist with lucide.

frontend/dist/assets/plus-Cw7xc8qj.js

@@ -0,0 +1,6 @@
+import{k as e}from"./index-C0Orcg9B.js";/**
+ * @license lucide-vue-next v1.0.0 - ISC
+ *
+ * This source code is licensed under the ISC license.
+ * See the LICENSE file in the root directory of this source tree.
+ */const a=e("plus",[["path",{d:"M5 12h14",key:"1ays0h"}],["path",{d:"M12 5v14",key:"s699le"}]]);export{a as P};