Push Notifications & SSO Invitation Fixes

Several fixes to make notifications and onboarding smoother.

What's improved

• Push for bot replies — When Kazo or other AI assistants reply to your message, you now get a push notification.
• SSO invitation flow — LINE users accepting community invitations now correctly link to their existing account instead of creating duplicates. The invitation redirect is preserved through the entire OAuth flow.
• Chat stability — Fixed query key conflicts causing stale data, added visibility-based reconnection, and push notifications now trigger a conversation refresh.