Centralize API v1 observability in Google Cloud

[anth-volk]

Summary

Integrate the Flask API v1 service with policyengine-observability 2.0 so requests produce centralized structured logs, traces, and bounded metrics in the policyengine-observability Google Cloud project.

Scope

• Configure an explicitly owned observability runtime during application construction.
• Instrument the Flask request lifecycle without route decorators.
• Propagate W3C trace context and X-PolicyEngine-Request-Id through the API v1 simulation dispatch path.
• Configure production and staging service identity, deployment environment, collector destination, and workload credentials.
• Prove API responses remain unchanged when observability setup or export fails.
• Preserve existing API contracts and calculation behavior.

Acceptance criteria

• API v1 request completion records use the version 2 schema.
• Simulation dispatch carries allowlisted correlation metadata only.
• Observability failures do not change successful responses or application exceptions.
• Production and staging deploy configuration names only the approved Cloud Run services and central destination.
• Relevant formatting, lint, unit, and contract checks pass.