fix(realtime): use 'event' instead of 'events' in postgres_changes protocol

[alexwhitmore]

What kind of change does this PR introduce?

Bug fix

What is the current behavior?

Fixes #1319

postgres_changes subscriptions always time out after 10 seconds and never receive payloads. The client sends events (plural) but the server expects event (singular), causing a protocol mismatch in three places:

1. binding_filter sends {"events": "*", "table": null} instead of {"event": "*"}
2. PostgresRowChange model expects events field but server returns event
3. channel.py compares server_binding.events which doesn't exist

What is the new behavior?

Subscriptions work correctly - state becomes SUBSCRIBED and payloads are received:

[2025-12-18 15:34:44.153631] Channel subscription state: RealtimeSubscribeStates.SUBSCRIBED

[2025-12-18 15:35:05.561223] *** RECEIVED PAYLOAD ***
{'data': {'schema': 'public', 'table': 'test_messages', 'commit_timestamp': '2025-12-18T14:35:05.504Z', 'type': <RealtimePostgresChangesListenEvent.Insert: 'INSERT'>, 'errors': None, 'columns': [{'name': 'id', 'type': 'int4'}, {'name': 'content', 'type': 'text'}, {'name': 'created_at', 'type': 'timestamptz'}], 'record': {'id': 16, 'content': 'testing fix', 'created_at': '2025-12-18T14:35:05.502162+00:00'}}, 'ids': [74307548]}

Additional context

Tested with local Supabase (realtime v2.67.2), Python 3.13.3, supabase-py 1.2.0.

Changes:

• types.py: binding_filter sends "event" key, only includes "table" if specified
• message.py: PostgresRowChange.events → event, table is now optional
• channel.py: server_binding.events → server_binding.event