Prepare v0.9.1 release

[terjekv]

Summary

Prepare the backward-compatible hubuum_client 0.9.1 patch release.

• bump the published crate and lockfile package version from 0.9.0 to 0.9.1
• move the accumulated Unreleased changes into the dated 0.9.1 changelog section
• update README installation examples and crate-level compatibility documentation
• add the required 0.9.1 compatibility record with pinned integration evidence

Compatibility

The declared target remains Hubuum server v0.0.9. The pinned OpenAPI contract remains at 202 operations, and the immutable required-test image remains:

ghcr.io/hubuum/hubuum-server@sha256:1f12baf882b6d3df5b4b2dbdf26aad0793274e57f86a2c186b8e1e68632db5db

The canonical Docker-backed library and independent e2e_client suites passed against that exact server image and the pinned PostgreSQL fixture.

Dependencies and MSRV

All direct and transitive dependencies were refreshed immediately before this release in #85. A new cargo update --dry-run --verbose reports zero additional Rust 1.88-compatible updates. cargo audit and cargo deny check bans licenses sources pass. The MSRV remains Rust 1.88 and every workspace target passes under that toolchain.

Breaking changes

None. No migration action is required.

Changelog

The dated 0.9.1 notes include JSON-path validation, server-advertised pagination limits, atomic export downloads, property-level OpenAPI reconciliation, the complete dependency refresh, the h2 advisory fix, and release-workflow security hardening.

Verification

• ./scripts/check-release.sh v0.9.1
• cargo run -p hubuum_reconcile --locked -- update
• cargo run -p hubuum_reconcile --locked -- check
• cargo fmt --all -- --check
• cargo clippy --workspace --all-targets --all-features -- -D warnings
• RUSTDOCFLAGS="-D warnings" cargo doc --workspace --all-features --no-deps
• cargo test --workspace --all-features --locked
• all five supported public feature combinations
• cargo +1.88 check --workspace --all-targets --all-features --locked
• python3 scripts/openapi-contract.py validate
• cargo update --dry-run --verbose
• cargo audit
• cargo deny check bans licenses sources
• cargo package --list -p hubuum_client
• ./scripts/run-integration-tests.sh --with-e2e-client -- --test-threads=1