ci: add conventional commit check and release please

[lhoupert]

Summary

This branch tightens release automation on `main` with Release Please, adds enforced conventional commits in CI and optionally via pre-commit (commit-msg), and documents the workflow for contributors. It also includes follow-up CI fixes, chart/version alignment for release automation, and dependency lock updates.

What changed

Conventional commits

• New workflow .github/workflows/commitlint.yml runs on every push (all branches) and validates commits in the pushed range with Commitizen (cz check), using uv run with a pinned commitizen==4.13.9.
• .pre-commit-config.yaml: commitizen hook on the commit-msg stage so invalid messages can be blocked locally after developers run pre-commit install --hook-type commit-msg.

Release Please + PyPI

• .github/workflows/release.yml: on push to main, Release Please opens/manages release PRs (uses release-please-config.json and .release-please-manifest.json). On release: published, the workflow builds artifacts and publishes to PyPI with OIDC trusted publishing (pypa/gh-action-pypi-publish).
• New Release Please config wires changelog (CHANGES.md, GitHub style), version bumps for root pyproject.toml, all subpackage __init__.py / pyproject.toml extras, Lambda Dockerfile, and Helm Chart.yaml (appVersion).

Helm chart independent versioning

• release-please-config.json: the Helm chart (deployment/k8s/charts/) is registered as a separate release-please package (release-type: helm). Its version: field in Chart.yaml is bumped independently from the Python package, driven by conventional commits that touch files under deployment/k8s/charts/. Helm releases are tagged helm-vX.Y.Z.
• deployment/k8s/charts/CHANGELOG.md: created as the changelog file required by the helm release type.
• .release-please-manifest.json: tracks the chart version (2.1.1) separately from the Python package version (2.0.0).

Docs & housekeeping

• RELEASING.md: fully rewritten to reflect the automated release process; replaces the old manual checklist with a description of the release-please flow, the independent helm chart release flow, and the commit convention table.
• CONTRIBUTING.md: guidance updated for the new commit/release expectations.
• pyproject.toml / package versions and chart/lambda metadata adjusted so Release Please can keep them in sync; uv.lock refreshed.
• Minor tweak in .github/workflows/check_charts.yaml.

Notes for reviewers

• Local enforcement: Commit message checks only run in Git hooks if pre-commit (including commit-msg) is installed; CI still enforces on push.
• After merge to main, confirm Release Please app/permissions and PyPI trusted publisher settings match this workflow.
• The Helm chart version: and the Python package version are intentionally independent: the chart only gets a new release when commits touch deployment/k8s/charts/. The appVersion: in Chart.yaml (which controls the default image tag) continues to track the Python package version automatically.

[github-actions]

⚠️ Performance Alert ⚠️

Possible performance regression was detected for benchmark 'TiTiler performance Benchmarks'.
Benchmark result of this commit is worse than the previous benchmark result exceeding threshold 1.30.

Benchmark suite	Current: f21acad	Previous: 4b5f858	Ratio
WebMercator response_time	0.03 s	0.02 s	1.50
WGS1984Quad response_time	0.04 s	0.03 s	1.33

This comment was automatically generated by workflow using github-action-benchmark.

[lhoupert]

@vincentsarago see explanation