feat(observability): correlated structured logs and full health

[Fluory]

Goal

Operations can follow one request through web, worker and AI service, and the health endpoint reports everything the pilot depends on.

Acceptance criteria

• Structured JSON logs (pino in TS, JSON logging in the AI service) with requestId, jobId, companyId
• Correlation ID propagated web → worker → AI service (X-Request-Id)
• /api/health adds queue backlog and AI-service reachability
• A test proves that a full synthetic run writes no document content or personal data to the logs

Not part of this task

• Central log shipping, alerting (production add-on)

Affected areas

• src/features/observability/
• src/features/jobs/
• services/ai/

Test plan

Criterion	Check
no PII in logs	integration test scanning captured log lines
health extensions	unit + integration test

Security/Privacy affected?

Logs are a data-leak path – IDs only.

Epic: #18 · Architecture: docs/decisions/ADR-0001-pilot-architecture.md

[Fluory]

Claimed by @Fluory (Claude Code, overnight run) on branch claude/feat-observability-28 – stacked on #27 (restacked before the PR). Code and tests are pushed.

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Generated by Claude Code