Release v1.2.0

Added

• EphemeralPostgres — spins up a throwaway Postgres container for integration tests and exposes connection_url().
• TestApp / TestAppBuilder — ephemeral axum test-server harness; builds a live server from a Router and returns a TestClient bound to it.
• SpanRecord / CaptureExporter / init_capture_tracing() — in-process OpenTelemetry span-capture helpers for asserting trace behaviour in tests.
• MetricsLayer / MetricsService — Tower middleware that records RED metrics (request count, error count, latency histogram) into a Prometheus registry.
• counter() — convenience constructor for a pre-registered Counter<u64>.
• socle::http_client module — trace-propagating reqwest client builder (builder(), ClientBuilder, Client) that injects W3C trace-context headers on every outgoing request.
• socle::openapi module — OpenAPI 3.0.3 helpers: merge_health_paths, rewrite_nullable_for_progenitor, to_3_0_pretty_json, and BearerAuthAddon.

Changed

• http_client implementation aligned with the service-kit reference implementation.