Add PR-time CI for build, lint, and typecheck

[Bre77]

Intent

• Add PR-time CI validation - build/typecheck currently only run during the publish pipeline on pushes to main, so a broken PR merges silently and only fails later at release time (found in the fleet CI audit).
  • Fix: new .github/workflows/ci.yml triggered on pull_request (and push to main) that runs install, lint, build, and typecheck across the monorepo.
  • Setup steps (pnpm version, Node version, pnpm cache) are copied verbatim from .github/workflows/publish.yml so the two workflows stay in sync. publish.yml itself is untouched.
  • Typecheck covers all 4 packages with TS: api, homebridge-teslemetry, n8n-nodes-teslemetry, node-red-contrib-teslemetry via pnpm -r --no-bail tsc, plus a dedicated step for iobroker.teslemetry, whose typecheck script is named check rather than tsc and is silently skipped by the recursive tsc invocation.
  • Lint: reuses the existing root pnpm lint (oxlint .) script - no new lint config added.
  • Scope boundary: this PR only adds CI wiring. It does not touch the publish workflow, lint config, or any package source.

What Changed

• Added .github/workflows/ci.yml.

Testing

• Ran every CI step locally against this branch before pushing: pnpm install --frozen-lockfile, pnpm lint, pnpm -r run build, pnpm -r --no-bail tsc, pnpm --filter iobroker.teslemetry check - all green.
• Will confirm the workflow itself runs green on this PR before merge.

Full narrative / original brief

[E10.1 follow-up, from the fleet CI audit] typescript-teslemetry: add PR-time CI.

The audit found build/typecheck only run during publish on main pushes - there is NO validation on pull requests, so a broken PR merges silently and only fails later in the publish pipeline.

Scope:

1. Add .github/workflows/ci.yml on pull_request (and push to main): pnpm install, build, and typecheck across the monorepo, covering all four packages that had TS7 failures: api, homebridge-teslemetry, n8n-nodes-teslemetry, iobroker.teslemetry (whose typecheck script is check, not tsc).
2. Reuse the setup steps (node version, pnpm version, caching) from the existing publish workflow so the two stay consistent - do not modify the publish workflow itself.
3. Include the oxlint run since a lint script exists in the root package.json; no new lint config.
4. Verify the workflow runs green on the PR before reporting done.