Migrate to cava-devops centralised CI/CD

[nicoloesch]

Changes in this PR

Migrates omop-llm from its old standalone semantic-release setup to cava-devops's centralized CI/CD, matching omop-emb/omop-graph/OMOP_Alchemy/orm-loader. CI/CD wiring only — no changes to the package's public interface (that's a separate, later PR).

• Deleted: release.yml, lint-pr.yml, .releaserc.json
• Added: ci.yml (no Postgres service — this package has no DB dependency), merge.yml, publish.yml, .github/release-drafter.yml, issue/PR templates
• Updated: docs.yml trigger to push: tags: ['v*'] + workflow_dispatch, pyproject.toml to hatch-vcs dynamic versioning (dev deps also moved from [dependency-groups] to [project.optional-dependencies], since the reusable docs workflow only reads that extra; added ty/ruff as new required dev deps)
• Frozen: CHANGELOG.md (header pointing to GitHub Releases)
• Fixed pre-existing ty/ruff violations blocking the new required checks (unsafe isinstance ordering, a couple of style rules) — no behavior change

Note

This is just preparatory work to resurrect omop-llm in pending work.