fix: outbound call — debounce customer-answered, auto-dispose on no-answer (#568)

Ozonetel sends 'in-call' even for voicemail (~4s before ACW), which
briefly enabled action buttons and poisoned wasAnsweredRef. Three fixes:

1. Debounce customerAnswered for outbound: require 'in-call' to hold 5s
   before enabling buttons (filters voicemail/IVR pickup)
2. Use live customerAnswered (not stale latch) for outbound call-end
   routing — unanswered calls go to Back to Worklist, not disposition
3. Auto-dispose with NO_ANSWER on unanswered outbound to release agent
   from ACW immediately (was waiting 30s for server safety net)

Also: hide AI FAB for CC agents in app-shell.

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

src/components/layout/app-shell.tsx

@@ -144,7 +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 />}
+                {isAdmin && !isCCAgent && <AiFloatingButton />}
             </div>
             <MaintOtpModal
                 isOpen={isOpen}