feat: global AI assistant floating button for supervisors (#578)

- AiFloatingButton: FAB (bottom-right) opens a slide-in drawer with
  the supervisor AI chat panel. Close button collapses drawer, FAB
  reappears. Chat state persists across open/close and page navigation.
- app-shell: mounts FAB for admin users (isAdmin), same pattern as
  CallWidget for agents.
- team-dashboard: removed inline AI panel + toggle button — replaced
  by the global FAB. Dashboard content reclaims the full width.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/components/layout/app-shell.tsx

@@ -15,6 +15,7 @@ import { useData } from '@/providers/data-provider';
 import { useMaintShortcuts } from '@/hooks/use-maint-shortcuts';
 import { useNetworkStatus } from '@/hooks/use-network-status';
 // import { GlobalSearch } from '@/components/shared/global-search';
+import { AiFloatingButton } from '@/components/shared/ai-floating-button';
 import { apiClient } from '@/lib/api-client';
 import { cx } from '@/utils/cx';
 
@@ -24,7 +25,7 @@ interface AppShellProps {
 
 export const AppShell = ({ children }: AppShellProps) => {
     const { pathname } = useLocation();
-    const { isCCAgent } = useAuth();
+    const { isCCAgent, isAdmin } = useAuth();
     const { isOpen, activeAction, close } = useMaintShortcuts();
     const { connectionStatus, isRegistered } = useSip();
     const networkQuality = useNetworkStatus();
@@ -143,6 +144,7 @@ export const AppShell = ({ children }: AppShellProps) => {
                     <main className="flex flex-1 flex-col overflow-hidden">{children}</main>
                 </div>
                 {isCCAgent && pathname !== '/' && pathname !== '/call-desk' && <CallWidget />}
+                {isAdmin && <AiFloatingButton />}
             </div>
             <MaintOtpModal
                 isOpen={isOpen}