fix: refresh token updates auth headers and sets realtime auth

[Kabya002]

This PR fixes an issue where Supabase Auth Admin API calls (and other client services) fail after the access token is refreshed via on_auth_state_change. The Authorization header was not being updated correctly, and Realtime auth was not being re-synced post-refresh.

Changes Made:

1. Implemented _listen_to_auth_events() method in both SyncClient and AsyncClient.
2. Subscribed to auth state changes with auth.on_auth_state_change(...) inside client constructors.
3. Updated Authorization headers when auth events like SIGNED_IN, TOKEN_REFRESHED, or SIGNED_OUT are triggered.
4. For AsyncClient, also called await self.realtime.set_auth(...) with the new access token.

Test Coverage:
Manually verified that:

1. Auth header updates after refresh.
2. Auth Admin API works post-refresh.
3. Realtime connections continue to work with the refreshed token.

Related Issue: Fixes #1143
(#1143)

[silentworks]

Hi @Kabya002 thanks for your first contribution. Can you provide some unit tests around the issue that this is fixing please?