docs: update CONTRIBUTING and README for automated dependency management and release process

[Amnoor]

Summary

This PR updates CONTRIBUTING.md and README.md to reflect the automated dependency management and release pipeline introduced in ci/dependabot-auto-release. Both documents now accurately describe the full end-to-end flow — from a Dependabot Node.js version bump through auto-merge, release branch creation, tagging, and GitHub Release publication — so that contributors and users have a complete and accurate reference.

Additionally, the table of contents has been removed from CONTRIBUTING.md as a housekeeping improvement, and the Release Process section has been rewritten to describe the new fully automated flow rather than the previous manual tag-push process.

Files Changed

Added:

• None

Modified:

• CONTRIBUTING.md
• README.md

Deleted:

• None

Key Changes

• Removed the table of contents block from CONTRIBUTING.md.
• Added a new Automated Dependency Management section to CONTRIBUTING.md documenting all four pipeline stages: Dependabot daily Docker monitoring, auto-merge on dependencies-labelled PRs, the release-from-develop workflow that constructs the release/v<semver>-<node_version> branch and opens a PR to main, and the tag-and-release workflow that creates an annotated Git tag and publishes a GitHub Release.
• Added a VERSION File subsection to CONTRIBUTING.md explaining that VERSION is the single source of truth for the SemVer component and that major or minor bumps require a manual update to VERSION before the next Dependabot cycle.
• Rewrote the Release Process section in CONTRIBUTING.md from a manual tag-push description to a numbered seven-step automated flow, ending with the deployment workflow publishing the multi-arch image to Docker Hub and GHCR with provenance attestations and an SBOM.
• Updated the closing line of Release Process from "can push tags to main and trigger a release" to "can merge the release PR into main and trigger a release", accurately reflecting the new flow.
• Added a new Automated Dependency Management & Release paragraph to the CI/CD Quality Guarantees section in README.md, describing the full automated pipeline — Dependabot → auto-merge → release-from-develop → tag-and-release — and noting that SemVer bumps require a manual VERSION file update.
• Fixed a missing trailing newline at the end of CONTRIBUTING.md.