feat: add floating call widget with SIP controls, click-to-call, and SIP provider

Introduce a shared SipProvider context so all components use the same SIP
connection. Add a floating CallWidget (idle pill, ringing, active with
disposition, ended states) visible for CC agents on every page. Add a
ClickToCallButton for the worklist. Wire SIP status badge and worklist
into the call-desk page.

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

src/components/layout/app-shell.tsx

@@ -1,6 +1,9 @@
-import type { ReactNode } from "react";
-import { useLocation } from "react-router";
-import { Sidebar } from "./sidebar";
+import type { ReactNode } from 'react';
+import { useLocation } from 'react-router';
+import { Sidebar } from './sidebar';
+import { SipProvider } from '@/providers/sip-provider';
+import { CallWidget } from '@/components/call-desk/call-widget';
+import { useAuth } from '@/providers/auth-provider';
 
 interface AppShellProps {
     children: ReactNode;
@@ -8,11 +11,15 @@ interface AppShellProps {
 
 export const AppShell = ({ children }: AppShellProps) => {
     const { pathname } = useLocation();
+    const { isCCAgent } = useAuth();
 
     return (
-        <div className="flex min-h-screen bg-primary">
-            <Sidebar activeUrl={pathname} />
-            <main className="flex flex-1 flex-col overflow-auto">{children}</main>
-        </div>
+        <SipProvider>
+            <div className="flex min-h-screen bg-primary">
+                <Sidebar activeUrl={pathname} />
+                <main className="flex flex-1 flex-col overflow-auto">{children}</main>
+                {isCCAgent && <CallWidget />}
+            </div>
+        </SipProvider>
     );
 };