bug(connections): connection pool does not classify or wrap connection failures

[ZhuchkaTriplesix]

PostgresConnectionPool.acquire and PostgresService._defaultCreateAndConnect let raw driver exceptions bubble up without classification. SSL, auth, network, and timeout errors all propagate as raw exceptions.

Impact: Callers (tree, workspace, stats) cannot provide targeted UX or diagnostics.

Expected: Wrap connection failures consistently, ideally with the typed exception from issue #256.

Acceptance criteria:

• Catch connection failures in createAndConnect and wrap in PostgresConnectionException.
• Ensure pool.acquire rethrows the wrapped exception.
• Add tests for fake factory failures.