Initial commit: VMware vSphere API simulator scaffold.

Add the FastAPI app, PostgreSQL migrations, Docker/Helm packaging, API
contracts, docs, client examples, and the unit/integration/compatibility
test suite for local client and tooling labs without a real vCenter.

docs/observability.md

@@ -0,0 +1,45 @@
+**Language / Язык:** [English](observability.md) | [Русский](ru/observability.md)
+
+# Observability
+
+## Health
+
+| Path | Meaning |
+|---|---|
+| `GET /health/live` | Process liveness — no dependency checks |
+| `GET /health/ready` | Database reachable via `database.is_ready()`; HTTP 503 when not |
+
+Example:
+
+```bash
+curl -sk https://localhost/health/live
+curl -sk https://localhost/health/ready
+```
+
+Implementation: [`app/observability/health.py`](../app/observability/health.py).
+
+## Request correlation
+
+Incoming requests accept or generate an ID via `REQUEST_ID_HEADER`
+(default `X-Request-ID`). Structured logs include correlation fields and
+redact known secret patterns (session ids, passwords, ticket-like tokens).
+
+## Metrics / tracing
+
+There is **no** Prometheus `/metrics` scrape endpoint and **no** bundled
+OpenTelemetry exporter in the current application. Architecture notes that
+mention them describe target design, not shipping telemetry.
+
+Do not confuse vSphere REST paths under `/api/vcenter/activity-history` or
+the seeded appliance health/timesync endpoints with simulator process
+telemetry — those handlers simulate vCenter appliance state inside
+PostgreSQL, not this process's own metrics.
+
+## Compatibility evidence
+
+Operational compatibility reports:
+
+- `/ui/api/compatibility?major=N`
+
+Also available through the Web UI compatibility panel. See
+[Compatibility](compatibility.md).