P2: Add structured metrics/logging for analysis initialization lock lifecycle

Problem

The analysis_zip.lock / analysis_zip.receipt coordination mechanism is opaque. There is no structured observability for lock acquisition, wait duration, reclaim attempts, or timeout exits. This made the 2026-08-04 stale-lock incident hard to detect early and difficult to quantify during response.

Proposed solution

Emit structured log events (key=value pairs or JSON) for each stage of the initialization lock lifecycle:

These events should be parseable by log aggregators (Vector, Loki, etc.) and ideally expose a counter/gauge for alerting on initialization stalls.

Acceptance criteria

• All lock lifecycle stages emit at least one structured log line
• Log lines include enough context to correlate across workers and analyses
• No sensitive data in log output
• Existing log output is not made significantly more verbose under normal conditions

Context

• Incident: 2026-08-04 OpenStudio Server queue stall

Locate the initialization code that coordinates analysis_zip.lock and analysis_zip.receipt, then trace acquisition, receipt detection, waiting, stale-lock reclamation, and timeout paths. Review the existing logging and metrics conventions before defining structured events with the listed correlation fields. Done means every lifecycle stage is observable, sensitive data is excluded, and normal log volume is not significantly increased.