refactor: centralise outbound dial into useSip().dialOutbound()

- Single dialOutbound() in sip-provider handles all outbound state:
  callState, callerNumber, outboundPending, API call, error recovery
- ClickToCallButton, PhoneActionCell, Dialler all use dialOutbound()
- Removed direct Jotai atom manipulation from calling components
- Removed setOutboundPending imports from components
- SIP disconnects on provider unmount + auth logout
- Dialler input is now editable (type or numpad)

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

src/providers/auth-provider.tsx

@@ -96,6 +96,12 @@ export const AuthProvider = ({ children }: AuthProviderProps) => {
     }, []);
 
     const logout = useCallback(async () => {
+        // Disconnect SIP before logout
+        try {
+            const { disconnectSip } = await import('@/state/sip-manager');
+            disconnectSip();
+        } catch {}
+
         // Notify sidecar to unlock Redis session + Ozonetel logout — await before clearing tokens
         const token = localStorage.getItem('helix_access_token');
         if (token) {