Fix PostgreSQL search rollout safety

[16francej]

Summary

• mark entry_search_text(text) parallel-unsafe, matching PostgreSQL's requirements for its exception handler
• extend the existing database safety regression to cover the search parser

Why

The v0.1.6 release candidate deployed successfully to Fly, but the live rollout gate rejected this function because it was declared PARALLEL SAFE. The declaration could also allow PostgreSQL to execute exception-handling PL/pgSQL in a parallel worker.

Validation

• reproduced the regression against a real local PostgreSQL database before the fix
• 57 PostgreSQL, search, and post-deploy smoke tests pass after the fix
• root TypeScript typecheck, targeted ESLint, Prettier, and diff checks pass
• deployed the exact patched source to qm-prod on Fly
• qm check --live passes: machine health, S3 round-trip, portal HTTP 200, database rollout checks, and private live-session smoke
• qm conformance passes

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