ci: bump pgpm to 4.33.0 and tune Postgres durability in CI

[pyramation]

Summary

Bumps PGPM_VERSION 4.7.4 → 4.33.0 in both workflows and adds a pgpm tune --yes step (new command, constructive-io/constructive#1336) right after pgpm install. It disables durability for the throwaway CI Postgres (fsync/synchronous_commit/full_page_writes = off, checkpoint_timeout = 30min, max_wal_size = 8GB) via ALTER SYSTEM + pg_reload_conf(), eliminating checkpoint I/O stalls on CI runners — the root cause of test flakiness fixed in constructive-io/constructive-db#1925 (flakiest shard: 644s → 110s).

Link to Devin session: https://app.devin.ai/sessions/7943c7526d254aa4828be110fbb3f272
Requested by: @pyramation

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