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/src/style.css

@@ -86,12 +86,14 @@ a { color: inherit; }
 a:focus { outline: 2px solid var(--accent); outline-offset: 2px; }
 
 /* Comfortable touch density + consistent transitions */
-button { min-height: 44px; transition: transform .15s ease, box-shadow .2s ease, background .2s ease, opacity .2s ease; }
+button { min-height: 44px; transition: transform .15s ease, box-shadow .2s ease, background .2s ease, opacity .2s ease; display: inline-flex; align-items: center; justify-content: center; gap: 6px; }
 button:not(:disabled):hover { box-shadow: 0 4px 12px rgba(20,24,40,.1); }
 button:not(:disabled):active { transform: scale(.97); }
 button.primary:not(:disabled):hover { box-shadow: 0 6px 18px rgba(79,70,229,.35); }
 button.soft { background: #f1f3f9; border-color: transparent; color: var(--ink); }
 button.soft:not(:disabled):hover { background: #e6eaf3; }
+/* Align inline SVG (lucide) icons inside buttons/links */
+button svg, .icon-btn svg, .brand svg { vertical-align: -2px; }
 
 input, select, textarea {
   min-height: 44px;