chore: migrate from Gitea to GitHub Actions exclusively

Remove Gitea workflows and consolidate to GitHub Actions as the single
CI/CD platform. GitHub is now the sole source of truth for the project.

Changes:
- Remove .gitea/workflows/ directory entirely
  - ai-review.yaml (Gitea-specific, not migrating)
  - e2e.yaml (replaced by .github/workflows/e2e.yaml)
  - release.yaml (already exists at .github/workflows/release.yaml)
- Migrate .gitea/workflows/ci.yaml → .github/workflows/ci.yaml
  - Add unit tests to CI workflow
  - Use Node.js 20 with npm caching
  - Add 10-minute timeout

GitHub Actions Workflows:
- ci.yaml: Lint, type-check, format-check, build, test
- e2e.yaml: End-to-end Playwright tests
- release.yaml: Build tarball, create GitHub release, update ArtifactHub metadata

Repository Setup:
- Single remote: https://github.com/cpfarhood/headlamp-polaris-plugin
- All development, CI/CD, and releases happen on GitHub
- ArtifactHub pulls releases from GitHub every 30 minutes

Generated with [Claude Code](https://claude.ai/code)
via [Happy](https://happy.engineering)

Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: Happy <yesreply@happy.engineering>

.gitea/workflows/ai-review.yaml

@@ -1,36 +0,0 @@
-name: AI Code Review
-
-on:
-  pull_request:
-    branches:
-      - main
-
-jobs:
-  ai-review:
-    name: AI Code Review
-    runs-on: ubuntu-latest
-    container:
-      image: catthehacker/ubuntu:act-latest
-    steps:
-      - name: Checkout code
-        uses: actions/checkout@v4
-        with:
-          fetch-depth: 0
-
-      - name: AI Review
-        uses: Nikita-Filonov/ai-review@v0.56.0
-        with:
-          review-command: run
-        env:
-          LLM__PROVIDER: "OPENAI"
-          LLM__META__MODEL: ${{ vars.AI_REVIEW_MODEL }}
-          LLM__META__MAX_TOKENS: "15000"
-          LLM__META__TEMPERATURE: "0.3"
-          LLM__HTTP_CLIENT__API_URL: "https://api.openai.com/v1"
-          LLM__HTTP_CLIENT__API_TOKEN: ${{ secrets.OPENAI_API_KEY }}
-          VCS__PROVIDER: "GITEA"
-          VCS__PIPELINE__OWNER: ${{ github.repository_owner }}
-          VCS__PIPELINE__REPO: ${{ github.event.repository.name }}
-          VCS__PIPELINE__PULL_NUMBER: ${{ github.event.pull_request.number }}
-          VCS__HTTP_CLIENT__API_URL: ${{ github.server_url }}/api/v1
-          VCS__HTTP_CLIENT__API_TOKEN: ${{ secrets.AI_REVIEW_GITEA_TOKEN }}