feat(postgrest): add client-level retry toggle (postgrest_client_retry)

[PhuocOng]

Closes #1561.

Adds postgrest_client_retry (default True) to ClientOptions, mirroring postgrest_client_timeout, and forwards it to the PostgREST client as a new retry_enabled constructor option. The flag propagates through schema(), from_()/table() and rpc() into every request builder, so postgrest_client_retry=False disables the automatic retry of transient PostgREST errors for the whole client. The existing per-request .retry() override still takes precedence.

No behavior change by default. _sync mirrors _async. sdk-compliance.yaml gets a note on database.configuration.auto_retry for the client-wide option.

Review guide: the logic lives in four files (postgrest/_async/client.py, postgrest/_async/request_builder.py, supabase/_async/client.py, supabase/lib/client_options.py); the _sync files are line-for-line mirrors, and the rest of the diff is tests.

Tests (TestRetryEnabled, async and sync): the flag propagates through from_/rpc/schema; and, with session.send patched to always answer 503, a client created with retry_enabled=False sends exactly one request, a per-request .retry(True) on that client sends 1 + MAX_RETRIES, and the default client also sends 1 + MAX_RETRIES. test_postgrest_client_retry_option covers the ClientOptions path in supabase. Locally: postgrest 210 passed (integration excluded), supabase 32 passed, mypy clean for both packages, ruff clean.