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>

.github/workflows/ci.yaml

@@ -0,0 +1,40 @@
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+jobs:
+  lint-and-test:
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: '20'
+          cache: 'npm'
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Build plugin
+        run: npx @kinvolk/headlamp-plugin build
+
+      - name: Lint
+        run: npx eslint --ext .ts,.tsx src/
+
+      - name: Type-check
+        run: npx tsc --noEmit
+
+      - name: Format check
+        run: npx prettier --check src/
+
+      - name: Run unit tests
+        run: npm test