feat: dynamic SIP from agentConfig, logout cleanup, heartbeat

- SIP provider reads credentials from agentConfig (login response)
- Auth logout calls sidecar to unlock Redis + Ozonetel logout
- AppShell heartbeat every 5 min for CC agents
- Login stores agentConfig in localStorage

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

src/pages/login.tsx

@@ -51,6 +51,13 @@ export const LoginPage = () => {
                 localStorage.removeItem('helix_remember');
             }
 
+            // Store agent config for SIP provider (CC agents only)
+            if ((response as any).agentConfig) {
+                localStorage.setItem('helix_agent_config', JSON.stringify((response as any).agentConfig));
+            } else {
+                localStorage.removeItem('helix_agent_config');
+            }
+
             loginWithUser({
                 id: u?.id,
                 name,