feat: 3-role auth, role-based routing, role-specific sidebar navigation

Add cc-agent role alongside executive and admin. Login page now has 3 tabs
(Marketing Executive, Call Center, Admin). RoleRouter renders the appropriate
home page per role. Sidebar shows completely different nav items per role with
role subtitle. Placeholder pages added for Team Dashboard, Call Desk, Call
History, and Follow-ups.

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

src/pages/call-desk.tsx

@@ -0,0 +1,15 @@
+import { TopBar } from '@/components/layout/top-bar';
+
+export const CallDeskPage = () => {
+    return (
+        <div className="flex flex-1 flex-col">
+            <TopBar title="Call Desk" subtitle="Manage inbound and outbound calls" />
+            <div className="flex flex-1 items-center justify-center p-7">
+                <div className="flex flex-col items-center gap-2 text-center">
+                    <h2 className="text-display-xs font-bold text-primary">Call Desk</h2>
+                    <p className="text-sm text-tertiary">Coming soon — call queue, dialer, and live call management.</p>
+                </div>
+            </div>
+        </div>
+    );
+};